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Quantum supremacy or advantage is fake.
Quantum teleportation is meaningless.
(Fig.1) The largest numbers factored so far by (still-useless) quantum computers is only 21 = 3 × 7 using fake (slower) Shor algorithm based on a single-world calculation
The current encryption system and keys such as RSA are based on two prime numbers or semi-primes, which are said to be cracked by (still-unrealized) quantum computers which may implement multiple simultaneous calculations of Shor's algorithm at once using (fictional) superposition = a dead-and-alive cat states or parallel worlds ( this p.4 ).
The point is all the current quantum computers are unable to correct errors, so they can Not calculate any meaningful values nor give right answers. ← Useful factoring by quantum computers or executing Shor algorithm is impossible (forever). ← There is No evidence of quantum superposition or parallel worlds causing quantum advantage.
So far, the largest numbers factored by the (still-useless) quantum computers are only 21 = 3 × 7 and 15 = 3 × 5 ( this 6th-paragraph, this 3rd-paragraph, this 4~5th-paragraphs ) using the fake modified version of Shor's algorithm (= called "semi-classical or Kitaev's (fake) Shor's algorithm" this 9, this 2-3rd paragraphs, this p.6 ).
↑ This fake Shor algorithm can carry out only one task at once using only one single world (= implement one task, reset, and recycle each quantum bit or qubit, this 14th-paragraph, this p.2 6th-paragraph,Fig.1.B-D this Figure.3,4,6,7 ) instead of implementing the dreamlike simultaneous quantum calculations which are required for faster factoring in true Shor's algorithm.
So the so-called post-quantum cryptography anticipating such an illusory quantum computers' threat or speed-up is completely meaningless ( this 4th-last~ 2nd-last paragraph, this 4~5th-paragraphs ).
Actually such dubious post-quantum encryption keys were easily cracked even by ordinary laptops or classical computers. ← The post-quantum encryption is useless, meaningless and just a waste of time.
As shown in the upper figure, when we try to factor 15 = 3 × 5 using Shor's algorithm, we first choose an arbitrary number (= for example, choosing "2" here ).
And then, we conduct multiple calculations like 21 divided by 15 gives the remainder of 2 (= 21 mod 15 = 2 ), 22 divided by 15 gives the remainder of 4, 23 divided by 15 gives the remainder of 8, 24 divided by 15 gives the remainder of 1,.. and find the period number (= 4, in this case ) which means the number of terms periodically giving and repeating the same remainders ( this p.7-12, this p.96 ).
↑ These simultaneous calculations giving multiple different remainders in Shor's algorithm need to be done by using (still-unrealized) quantum computer's fictional superposition ( this Step.6, this p.9, this p.2-last-paragraph ) or parallel worlds ( this last-paragraph, this 19-20th paragraphs, this last-paragraph ) in order to factor large numbers faster and break the current encryption key system ( this 10th-paragraph ).
↑ In order to unrealistically carry out these multiple different simultaneous calculations for factoring large numbers using Shor algorithm on the same common quantum bits or qubits, not only qubits but also the external devices emitting microwave pulses for manipulating qubits have to be unrealistically split into multiple different parallel worlds ( = one microwave pulse must split into multiple microwave pulses existing in different parallel worlds to simultaneously calculate different parallel-world numbers by manipulating qubits existing in different parallel worlds ), which is impossible also in the original quantum mechanical rule.
Using the period "4" allegedly found by performing multiple (parallel-world) calculations, we can obtain two prime numbers (= 24/2 - 1 = 3, and 24/2 + 1 = 5 ) composing 15 = 3 × 5 ( this p.13-14 ).
↑ Contrary to the media-hype baselessly saying like "Quantum computers will be exponentially faster", the current useless quantum computers can Not carry out these simultaneous quantum mechanical calculations (= giving multiple different remainders using different parallel worlds simultaneously by Shor algorithm is impossible in the current useless quantum computers ), instead, they can only do one single simple task using fake slower Shor's algorithm needing the help of traditional classical computer or algorithm ( this p.3-first-paragraph,p.23-2(b) ).
It means thinking about the post-quantum encryption prepared for the fictional quantum computers' power of simultaneous calculations using imaginary parallel worlds is nonsense, and just a waste of time and money.
(Fig.2) Using fragile photons or very weak classical lights as quantum information, which is easily destroyed by eavesdropper, is impractical
Quantum network, information, cryptography and key distribution (= QKD ) use a very fragile photon or very weak light as a carrier of quantum information, which is completely useless ( this p.1-introduction, this p.2-left-last-paragraph ).
For example, light's vertical V (or horizontal H ) polarization is used as a bit's information of "0", and horizontal (or vertical ) polarization is used as "1" ( this p.2-Fig.1 ).
In other methods of encoding quantum information into the photon's time bin or light phases, the photon or weak light pulse arriving earlier is used as a bit's information "0". and a photon or weak light pulse arriving later is used as "1" ( this p.2 ).
There is No such thing as a photon.
Physicists just use the attenuated laser light as fictitious photons. ← Generating a single photon at the designated time is impossible ( this p.2-4th-paragraph, this p.6 ).
When some eavesdropper tries to steal this fragile photon's information, the photon or weak light is easily destroyed or changed by the eavesdropper, which destroyed photon or light can be detected as a sign of eavesdropper ( this 2nd-paragraph, this 1st-paragraph, this 4th-paragraph ).
↑ Very weak classical light instead of (fictional) photons can be used as a means to detect eavesdroppers, so quantum mechanics is unnecessary for quantum cryptography or quantum key distribution's overhyped "unhackable security" .
This fake secure quantum cryptography is useless, because if some eavesdroppers or other noises constantly intercept or influence this fragile quantum information or weak photons, the photons or weak lights are easily and constantly destroyed, and sending quantum information itself is impossible.
This quantum key distribution (= QKD ) sending very fragile photons or weak light is impractical, unable to send information stably over long distance ( this p.1-last-paragraph ).
This 5th-paragraph says
"quantum theory.. ensures that any attempt at eavesdropping on the channel results in a modification of the qubits (= destruction of fragile photons or weak light by eavesdroppers ), which will be detected by Alice and Bob. Therefore, QKD offers a secure way to exchange cryptographic keys. However, because qubits cannot be amplified, there are physical limitations on the distances between links. Most commercially available systems have a range of around 100km"
So quantum cryptography or quantum key distribution is completely useless, trying to get meaningless security by using easily-broken photons or weak light as information carriers, sacrificing transmitting distance and practicality.
Quantum information comprised of very faint photons or light is easily destroyed and lost.
But quantum mechanical stupid rule unreasonably forbids such fragile photons or weak light from being copied and amplified ( this p.11 ).
So it is impossible to send quantum information over long distance (= successful key generation rate over 200km is extremely low, and almost all photons easily get lost, this p.34 ).
This 2nd-paragraph says
"One of the most significant challenges is to extend the distance of quantum communication to a practically useful scale. Unlike classical signals that can be noiselessly amplified, quantum states in superposition cannot be amplified"
Due to this extremely low success rate of sending fragile photons, it takes extremely long time for a receiver to get information ( this 1st-paragraph ).
This p.1-introduction-3rd-paragraph says "Current distance record in fiber for QKD (= quantum key distribution ) is 404 km. At a distance of 1000 km fiber, one would detect only 0.3 photons per century (= due to massive photon loss ) even with 10 GHz ideal single photon source (= even when 109 photons per second or 10 GHz are generated, it takes a century for only 0.3 photons out of them to reach destination over 1000 km, and almost all other photons are lost ),
".. the key rate, however, will still drop down dramatically in long distance. One solution to this challenge is quantum repeater.. its real application still suffers from the limited performance of quantum memory."
The problem is the quantum information or fragile photons sent to the receiver always includes errors (= there is always disagreement between a sender's and a receiver's quantum information ), which can Not be used as legitimate quantum key.
In order to correct these errors, sending errorless information via the ordinary classical communication is indispensable after all, which is called "reconciliation ( this p.6-lower )."
This middle says
"While in practice, bit error rate (BER) is not necessarily associated with vicious eavesdropping. Detection inefficiency, transmission loss, imperfect entanglement sources and many other factors contribute as false alarms. Error correction is an essential post-processing procedure."
↑ The fact that sending information by classical channel is necessary to correct errors ( this p.2-left-2~3rd-paragraph ) means quantum cryptography or quantum key distribution relying on quantum channel as a reason for security is meaningless.
Sending fragile photons or quantum information cannot use the ordinary telephone lines, because noise easily causes errors in quantum information.
They need to prepare different independent fiber lines for different senders and receivers, one-to-one, which needs infinite numbers of lines for many users, hence impractical ( this p.6-left-1., this middle-1. ).
This-middle Can QKD be deployed on a large scale ? says
"its point-to-point nature,.. make its large-scale deployment extremely complex and costly
The alternative of directly linking all nodes that need to communicate is not feasible"
This 5th-paragraph says
"The problem is that the sites that wish to engage in quantum cryptographic communication must be directly connected by a quantum key distribution system.
Widespread real-world deployment of quantum cryptographic communications would require the installation of a prodigious number of quantum key distribution systems directly connecting every site. This is simply not practical."
As a result, all the quantum cryptography, key distribution, internet and network are unrealistic, impossible forever, contrary to the hype.
(Fig.3) The allegedly secure quantum key distribution can be explained by classical very weak polarized light. No quantum mechanics is necessary.
The upper figure shows the original quantum key distribution (= QKD ) protocol called BB84 ( this-middle-lower ).
In this QKD protocol, Alice (= sender ) is supposed to send four kinds of (classical) very weak lights or photons with polarizations of ① vertical (= 0 ), ② horizontal (= 1 ), ③ 45o (= 0 ) or ④ 135o (= 1 ) angles, randomly and repeatedly to Bob (= Alice records what polarized lights are sent ).
Bob chooses one polarization filter or a polarizer (= basis ) of rectilinear (= parallel to vertical or horizontal polarization ) axis or diagonal axis (= parallel to 45o or 135o ).
When Bob chooses the rectilinear polarizing filter, the ① vertically-polarized light ( or ② horizontally-polarized light ) can 100% pass (or is 100% reflected from ) this rectilinear filter and is detected by the light or photon detector as "0 (= pass)" or "1 (= reflect )" without the incident light splitting at the polarizer.
But if Bob chooses the diagonal polarizing filter, the ① vertically-polarized light (= 0 ) may split into two weaker lights into "pass (= 1 )" and "reflect (= 0 )" sides, which can give wrong answers or errors ( this p.1-2 ), because Alice sends quantum information of "0" as vertically-polarized light, but Bob may mistake it for "1" due to the wrongly-chosen polarizer or basis.
↑ In this case, the originally very weak light or photon is split and far weaker by the polarizer, so only one (or zero ) weaker light on the side of "pass" or "reflect" can narrowly exceed the detection threshold of the photodetector and is detected as a (fictitious) photon.
Later, Alice and Bob have a talk with each other through ordinary classical channel, and choose only the cases of the same polarizing filters or the same basis chosen (= the case where Alice sends vertically or horizontally- polarized lights, and Bob chooses rectilinear polarizing filter, or the case where Alice sends 45o or 135o-polarized lights, and Bob chooses diagonal polarizing filter ).
↑ Eavesdroppers, who don't know which polarizing filter Bob will choose, may send wrongly-polarized lights, after the eavesdroppers detect lights or photons with some randomly-chosen polarizing filters ( this p.1-2.BB84 protocol ).
↑ This is the mechanism of finding eavesdropping.
As seen here, this mechanism of secure quantum key distribution or cryptography can be explained by classical weak light (= which can be split at the polarizing filter and detected by photodetector only when it's light intensity exceeds the detection threshold ), and quantum mechanics and photons are unnecessary.
As I said, this quantum key distribution based on very fragile photons or very weak light is impractical, error-prone, unable to send information stably and correctly.
In actual experiments, encoding quantum information of 0 or 1 in the polarization of weak light or a photon is difficult.
So they often use the time-bin or light phase-encoding where the early-arriving light pulse (= corresponding to a bit = 0 ) and the late-arriving light pulse (= a bit = 1 ) are used as carriers of quantum information.
In this experiment ( = p.2-Figure 1 ), they encoded quantum information 0 or 1 in four different weak lights or photons with different phases (= different arriving time ) of 0 phase (= bit 0, basis-1 = polarizing filter-1 ), π/2 phase (= bit 0, basis-2 = polarizing filter-2 ), π phase (= bit 1, basis-1 = polarizing filter-1 ) and 3π/2 phase (= bit 1, basis-2 = polarizing filter-2 ), and could not send over 200 km (= p.5-Figure 5 ), useless.
In the first quantum key distribution experiment, very weak light with rectilinear or circular (= left-handed or right-handed-circularly-polarized light instead of 45o or 135o polarization ) polarization was sent over only 32cm with success rate of just 0.75% (= less than one photon could reach the detector 32 cm away, when 100 photons were sent ) with errors. ← Far from a practical communication.
This p.10-4th-paragraph says "The quantum channel itself is a free air path of approximately 32cm (= too short )"
↑ This original paper ↓
p.4-lower says "Realistic detectors have some noise, which cause errors.. Producing a single photon is impossible (= so the attenuated laser light was used as a unseen fictitious photon )."
p.6-last-paragraph says "circularly-polarized light was used instead of diagonal polarization (= this case also can be explained by classical weak light )"
p.10-4th-paragraph says "640 light or photons out of 85000 generated light pulses were received by Bob with error rate of 4.375% (= even the 640 sent photons included 4.37% errors that must be fixed by classical communication after all, quantum information was meaningless )"
↑ So the success probability of sending fragile photons or quantum information over only 32cm was just 640/85000 = 0.0075 = 0.75% (= 99.25% photons were lost. Very inefficient ).
The recent quantum key distribution experiments showed very low success rate of sending quantum key = only 0.25 photon or quantum key bit per second could reach the receiver's detector over 421km, even when 2.5 × 109 photons per second (= 2.5 GHz = 2.5 × 109 Herz, 1 Herz or 1 Hz means one photon per second ) were generated and sent, which is too low success rate to be practical.
This 2nd-paragraph says
"A major obstacle is posed by the fact that most photons are scattered or absorbed before getting to the receiver. In a standard optical fiber, a photon’s chances of survival are 10% after 50 km and fall to only 0.01% after 200 km (= 99.99% of the sent photons or quantum information was lost over only 200 km )"
"This is devastating considering that standard optical repeaters can’t faithfully regenerate a quantum signal, and quantum repeaters are still beyond today’s technological reach"
"Even with large signal loss, the count rate in Bob’s detectors can exceed a thousand counts per second if billions of photons are transmitted every second (= this success probability of sending photons is only 1000/1000000000 = 0.000001 = only 0.0001 %, which is impractical and too slow to send information )"
↑ This original paper ↓
p.1-right-3rd-paragraph (or p.1-left-3~4rd-paragraphs ) says "Alice uses a phase-randomized diode laser pulsed at 2.5 GHz (= 2.5 × 109 Herz ). Phase randomness is achieved by switching the current completely off between the pulses (= Alice sent 2.5 billion photons with phase or time-bin-encoding per second to Bob )"
p.3-Table I (or p.3-right-last-paragraph) shows SKR (= secret key rate, this p.6-3 ) over 421 km is only 0.25 bps (= bit per second ), which means only 0.25 bits or 0.25 photons could reach the receiver's detector per second.
↑ It means the success rate of sending photons or quantum information over 421km is only 0.25/(2.5 × 109 = 2.5 GHz ) = 10-10 = 0.0000000001. ← Too low success rate, and quantum key distribution and quantum internet are impractical forever, contrary to hypes.
The so-called twin-field quantum key distribution (= TF-QKD ) means two different persons A and B send two independent information or photons to the middle-point between A an B with very low success rate, which means the actual distance they send information is just half (= in 830km twin-field quantum key distribution, each A or B sends photons or information over only 415km = 1/2 × 830km, ← Not 830km, this Long range-3rd-paragraph ).
This latest (impractical) research on twin-field quantum key distribution ↓
p.3-last says "The signals (= laser lights or photons ) are then attenuated to the predetermined intensities and subsequently transmitted to Charlie (= middle point between senders of Alice and Bob ) via the quantum channels"
p.4-right-2nd-paragraph-Result says "The fibre distances between Alice-Charlie and Bob-Charlie are measured to be 500 km and 502 km (= actual distance of the sent photons is 500km = half of the overall 1000 km )"
p.5-left-3rd-paragraph says "Owing to the significant optical attenuation (= photon loss ) experienced over long-distance fibre, it is necessary to send a larger number of quantum signals.. The final secure key is 3.11 × 10-12 (= success rate of sending photon information is only 0.00000000000311, too bad, p.4-Figure.3 ), which equates to 0.0011 bps (= they could send only 0.0011 photon bits per second, or only one photon bit information per 1000 seconds, too slow )"
(Fig.4) Only one pair of polarized lights or photons could reach ground stations out of 5.9 million pairs of photons emitted by a satellite, which was too low success rate.
Sending fragile quantum information or very weak light (= photon ) by satellites is also impractical ( this p.1-left ).
This p.1-2nd-paragraph says
"The main challenge of long-distance free-space quantum communication are the high
photon losses in the channel, caused mostly by absorption, diffraction and turbulence in
the air"
Due to a lot of background noise or irrelevant lights, quantum information can be sent only during the night in fine weather between a satellite and isolated ground stations at the high altitude (= they cannot send information or photons to towns or in daytime due to much more irrelevant lights and background spoofing it ).
This p.4-2nd-paragraph says
"Quantum repeaters are still the subject of fundamental research and not practical at present.
An alternative is to use satellite-based QKD. However, current implementations mostly target nongeostationary orbits so that the availability of these satellites, which is also sensitive to weather conditions,
is limited to a short timeframe per day. This further limits the practical key rate"
In the recent experiment using Chinese satellite, about 5.9 million pairs of photons or two weak lights per second (= 5.9 MHz, one light is horizontally-polarized and the other light is vertically-polarized in each pair ) were emitted from a satellite toward two separate ground stations which were about 500 ~ 1600 km away from the satellite.
And only about one pair of photons (= 1.1 photons or 1.1 Hertz, this-4th-last-paragraph ) per second were successfully detected by two ground stations (= when one ground station detected a horizontally-polarized light, the other ground station detected a vertically-polarized light, which they called "entanglement" that has nothing to do with superluminal spooky link ).
↑ One photon pair/5.9 million pairs of photons sent = 0.00000017 (= success probability ) ← This was too low success rate to be useful.
↑ This original paper ↓
p.2-left-2nd-paragraph says "the distance between the satellite and two ground stations at an altitude of about 3000m" is 500~2000km.
p.2-left-3rd-paragraph says "we established entanglement between two single photons.. with an average two-photon count rate of 1.1 Hz and state fidelity of 0.869 (= which means even the sent photons that reached ground stations only one time per second showed the error rate of 0.131 or 13.1% error, which cannot be used as practical key )"
p.2-left-last-paragraph says "The source emits 5.9 million entangled photon pairs per second (= entangle means just a pair of photons; one light is vertically-polarized V and the other light is horizontally-polarized H, No superluminal spooky link )"
p.3-right-1st-paragraph says "the background noise ranged from 500 to 2000 counts/s in each detector (= which caused errors that must be corrected by ordinary classical communication, so quantum information is meaningless )"
↑ The total success probability of sending pairs of photons to two ground stations from the satellite is only 1.1/5.9 million = 0.00000017, which is too bad and too slow to use as practical communication or internet.
(Fig.5) Quantum repeater just tries to detect two photons or weak lights simultaneously (= Bell state measurement BSM ), which is very low success rate, and impractical
As I said, fragile quantum information consisting of photons or very weak light easily gets lost, but quantum mechanical unphysical rule forbids quantum information or photons from being copied or amplified.
Only way to send such fragile attenuating quantum information or photons over long distance is said to be quantum repeater ( this-lower-Figure 4 ).
But this quantum repeater is also useless and unable to send quantum information over long distance after all.
In order to send quantum information by the quantum repeater, multiple light sources (= S1 ~ S6 in the upper figure ) must emit pairs of photons or weak polarized lights (= ex. one light is horizontally-polarized H light, and the other light is vertically-polarized light V, which they call entanglement, but entanglement itself is a meaningles concept sending nothing ).
And multiple light detectors have to detect all those photon pairs simultaneously (= called Bell state measurement BSM or entanglement swapping ).
For example, in the upper figure, when the photodetectors (= b ) simultaneously detect a pair of photons comming from S1 and S2 sources as the same polarized lights (= ex. one light is vertically-polarized V2, and the other light is also vertically-polarized V3 ), it means two other photons with the same horizontal polarizations = 1H (= horizontal ) and H4 (= horizonal ) reach the sender (= a ) and the distant position (= c ).
↑ So two distant positions of "a" and "c" can obtain light or photons with the same polarizations (= ex. horizontal H ), when the middle photodetectors (= b ) detect a pair of lights or photons with the same polarizations (= ex. vertical V ), which is the mechanism of the (impractical) quantum repeater consisting of multiple light sources and detectors without amplifying weak light.
The quantum repeater just measuing a pair of weak photons also cannot amplify the attenuating weak photon information.
The problem is the success rate of detecting two photons in each detectors BSM (= which they call entanglement, No spooky action ) is extremely low = less than 1/1000.
This means the total success rate of three pairs of light detectors detecting three pairs of photons is almost zero = 1/1000 × 1/1000 × 1/1000 = 0 (= simultaneous detection of multiple weak photons is impossible due to extremely low success probability ), which quantum repeater is also unable to send quantum information over long distance after all.
Quantum memory, which can transiently absorb the photon or light's energy in atomic excited energy levels, is also error-prone and useless.
This 2.State of the art-5th-paragraph says
"However, building them requires functional quantum memory that is Not yet available. Therefore, quantum repeaters have Not yet appeared"
And all the above light (or) photon sources (= S1,S2,S3.. ) need to know what information must be sent beforehand through ordinary classical communication, which makes quantum communication meaningless (= or individual photon sources S1,S2,S3 just emit lights with random polarization, which takes too much time to coincide with the sender's light polarization accidentally ).
Even in the latest repeater experiment, physicists could only connect two positions separated by just 50km.
They used two ions A and B trapped in the same middle point, these ions emitted photons or lights, whose polarizations changed depending on which energy levels inside an ion emitted the photons.
These lights or photons emitted from two ions A and B went to two different positions (= separated by 50km ) which are 25km away from the middle point of two ions.
And the later measurement of these two ions' energy levels determined what polarization two sent lights had (= and this measurement related two sent photons or lights with each other ), which they called entanglement or quantum repeater.
The total success probability of detecting two photons emitted from ions A and B after traveling 25km is only 9.2 × 10-4 ( this p.3-left, or this 6th-paragraph ) = about 1/1000 (= 99.9% photons or lights emitted from ions got lost ).
↑ This means the success probability of sending fragile photons over longer distance needing more repeaters becomes 1/1000 × 1/1000 × 1/1000 ... = 0.
As a result, even quantum repeaters cannot send fragile quantum information or photons over long distance.
↑ As this 6th-paragraph says, this latest quantum repeater's error rate or fidelity was 0.72 (= error rate = 1 - 0.72 = 0.28 = 28% ).
↑ This is too high error rate to send precise quantum key or information, and these errors caused by quantum repeaters must be corrected by ordinary classical communication, so the original goal of sending quantum information via secure quantum channel was meaningless.
Quantum memory can store information for only very short time (< 1ns ), and loses 87% photons or information (= memory efficiency is only 12.9%, this p.3-right-3rd-paragraph ), which is a completely useless memory.
The 1st, 4th, 7th, 8th, 10th, last paragraphs of this hyped news say
"Researchers.. have demonstrated that advanced quantum-based cybersecurity can be realized in a deployed fiber link (= wrong. Researchers just sent fragile weak light wave or photons over only 5km short distance with No tests of cybersecurity = still No practical use )."
"The signal traveled across ORNL's fiber-optic network encoded in continuous variables that described the properties of light particles, or photons, in amplitude and phase (= utilizing wave amplitude and phase means a photon is just a weak classical light wave, Not a particle )"
"Quantum key distribution is a cryptographic protocol where two parties can generate a secure key that only they know,.. In this experiment, this is done by using lasers to generate weak optical pulses (= just laser light wave, Not a photon particle ) between two points, usually referred to as Alice and Bob."
"When the receiving party measures a pulse, measurements can reveal whether an eavesdropper intercepted and corrupted the message (= this quantum cryptography or cybersecurity mechanism can be explained by weak classical light wave whose destruction tells us whether the light is eavesdropped on or not, which does Not need a fictional quantum photon, this-1st-paragraph )"
"Excess noise erodes the rate of the key that can be distributed. Too much noise,.. (= quantum key using weak light is vulnerable to noise )"
"Future efforts will (= just speculation, practical quantum key distribution is still unrealized ) focus on reproducing the experiment's results under a wider range of network scenarios."
↑ This research tried to send weak light pulses (= Not a photon particle ) to a detector at a distance of 5km, and only 0.16 % of those sent lights whose phases were used as information arrived at the detector (= most of lights or photons were lost and unrecoverable ), which is impractical as internet or network.
↑ This research paper ( this ↓ )
p.1-left-3rd-paragraph says "A major technical challenge in CV-QKD (= Continuous-variable quantum key distribution ) detection is carrier phase recovery: to reliably decode the information encoded on field quadratures" ← quantum key distribution is still useless with a lot of challenges
p.3-right-1st-paragraph says "generate 12 ns-wide pulses at a 1 MHz repetition
rate (= 106 light pulses per second were sent ). These pulses pass through polarization-maintaining
optical fiber"
p.5 Weak light or photons were sent through the 5km optical fiber.
p.7-Table I shows says key rate is 1.6 kbps over 10km (= success rate of sending photons or quantum information over 10km is only 1600/1000000 = 0.0016 = 0.16% ) which cannot send important information reliably
↑ Just sending light or information over the short 10km lost 99.9% of them (= unrecoverable ), so stably sending secure quantum information over practically-long distance is just a pipe dream ( this p.6-Fig.4 ).
Contrary to the hypes, all the quantum information technologies such as quantum key distribution, internet, network, cryptography are already deadend with No progress or No hope of utility.
Quantum internet has to rely on very weak light or photon whose wave phase or polarization is used as information, and quantum mechanical stupid rule forbids researchers from copying and amplifying the weak light 's information ( this 2nd-paragraph ).
As a result, it is impossible to send the very weak light or quantum information over long distance required for practical internet ( this-lower challenge of quantum network, this p.1-left ).
This 2nd, 5-6th paragraphs say
"First, the quantum internet relies on the transmission of single photons that cannot be amplified or split. Without amplification, these signals diminish within 100 km or less of their source. Therefore, optical loss and noise present much bigger problems for the quantum world."
"storing photons is still a big challenge"
"the biggest challenges involve the emission of single photons and their transport over long distances." ← still impractical quantum internet.
Quantum repeater unable to amplify the light information just sends two weak lights with the same (or perpendicular ) polarization (= which they call entanglement that means classical lights with some correlated polarizations unrelated to quantum mechanics ) to two distant places and detects them simultaneously (= No quantum mechanical superluminal link ).
↑ Success rate of detecting these two weak lights simultaneously is only 0.00092 (= 9.2 × 10-4 ) over only 50 km distance (= which means almost all weak lights or photons are lost even using quantum repeaters which cannot solve the issue of fragile photons in quantum internet, this-5~6th-paragraphs, this p.3-left ).
So like useless overhyped quantum computers, quantum internet (= still far from actual internet ) and key distribution are also impractical pseudo-science just wasting researchers' time and taxpayers' money.
The 3rd, 6-7th, last paragraphs of this hyped news say
"Entangled photons are particles of light that remain connected, even across large distances, and the 2022 Nobel Prize in Physics recognized experiments on this topic.. the IQC research team aimed (= meaning "still unrealized" ) to optimize the process for creating entangled photons, which have a wide variety of applications, including secure communications (= false, entanglement is useless )."
"By embedding semiconductor quantum dots into a nanowire, the researchers created a source that creates near-perfect entangled photons 65 times more efficiently than previous work (= still impractically-low efficiency even in this latest research, though )."
"This new source.. can be excited with lasers to generate entangled pairs on command (= false, efficiency of creating these correlated lights or illusory entanglement is still extremely low, Not on command ). The researchers then used high-resolution single photon detectors (= a fictitious photon itself is undetectable, they just detect electrons excited by light )"
"Using their new quantum dot entanglement source, the researchers simulated a secure communications method known as quantum key distribution (= just simulation, Not experimental realization ), proving that the quantum dot source holds significant promise in the future (= just speculation, still useless ) of secure quantum communications."
↑ This research just let quantum dot (= artificial atom ) emit two (classical) lights (= or photons ) with the same polarization (= HH ), which they called entanglement using fictitious exciton quasiparticle ( this p.2-Fig.1 ), and detected them simultaneously with impractical low efficiency that prevents precise communication. No quantum mechanical prediction nor practical application.
↑ This research paper ↓
p.1-left says "Developing a bright, deterministic source of entangled photon pairs for
applications in photonic quantum information.. has
been a long-standing scientific and technological challenge" ← It means quantum information, entanglement are still useless, illusion.
p.1-right-2nd-paragraph says "quantum key distribution
(QKD) protocol allows all photon pairs emitted from the biexciton-exciton (= fictional quasiparticle )
cascade to generate a secure key,. To estimate
the potential key rates" ← this research just simulated or estimated QKD, No experimental realization.
p.5-right-Tomography apparatus says "apparatus was used to
maintain the nanowire sample at 4.5K (= impractically-low temperature )"
p.6-left-source efficiency says " The total optical efficiency after the 70:30
beamsplitter to the SPAD (= single photon avalanche diodes ) detector after the
spectrometer was estimated to be 2.41 ± 0.07% (= only 2.41% photons or lights were left, all other 98% photons or information were lost )"
"pair extraction efficiency at the first lens of 0.65 ± 0.02%"
↑ "Extraction efficency" is the proportion of photons generated in the quantum dots that escape from the device ( this-middle ), which was just 0.65% ( this p.2-lower-p.3 ), which means almost all photons or lights (= 99.35% ) having information as light polarization were lost when they escaped from quantum dots ( = photon-pair source efficiency is very low, only 0.0037, this p.17-5th-paragraph ).
Quantum entanglement means just simultaneous measurement of two (classical) lights or photons' polarizations (= ex. when one light has horizontal polarization, the other light always has horizontal polarization, = HH ), which can neither send real information nor secure communication, as seen in still-impractical quantum key distribution.
Quantum information carried by (fictional) photons or weak light's polarization easily gets lost ( this 7th-paragraph, ).
The successful rate of sending and detecting (allegedly-entangled) photon pair over only 50km is extremely-low, only 0.00092 or 9.2 × 10-4 ( this 6th-paragraph, this p.6-Fig.4 ), which means the successful rate of sending photons or quantum information over longer distance is hopeless, much much lower (= 0.00092 × 0.00092 ×.. ).
↑ Practical internet or communication needs 100% successful rate of sending information, so quantum communication trying to use fragile photons or weak light at extremenly low temperature (= 4K ) and extremely high photon information loss rate is completely useless.
Nobel prize is often used as a political tool to justify and enable impractical science to get taxpayers' money as research funds, as seen in unrealistic entanglement, (parallel-world) quantum computers and harmful vaccines.
The 1-2nd, 7th, 11th, 15-16th paragraphs of this hyped news say
"Researchers at DTU have successfully distributed a quantum-secure key using a method called continuous variable quantum key distribution (CV QKD). The researchers have managed to make the method work over a record 100 km distance—the longest distance ever achieved using the CV QKD method (= No progress, and just 100km is useless as internet or network )"
"Quantum computers threaten existing algorithm-based encryptions, which currently secure data transfers against eavesdropping and surveillance. They are Not yet powerful enough to break them (= quantum computer is also useless, No progress )."
"When a sender sends information encoded in photons,.. Attempts by others to measure or observe photons in a quantum state will instantly change their state. Therefore, it is physically only possible to measure light by disturbing the signal (= eavesdropper's measurement can be detected by the disturbed classical weak light, so this quantum key distribution mechanism does Not need quantum mechanics )."
"It works by sending data via infrared light (= just classical light wave or attenuated laser, Not a fictitious photon particle ) running through optical fibers."
"Furthermore, the researchers have become better at correcting errors that can occur along the way, which can be caused by noise, interference, or imperfections in the hardware (= this correction of erroneous, useless quantum key needs ordinary classical communication between senders and receivers, so quantum key distribution is meaningless after all )"
"In our upcoming work, we will (= just speculation, still useless ) use the technology to establish a secure communication network"
This research just sent weak light wave or fictitious photons (= light phase encodes information 0, 1 ) over only 100 km, and almost all lights or fragile photons were lost.
↑ Quantum information or photons decreased to less than 1/1000 over only 100 km (= sending information or photons over 120km was impossible ).
This p.4-Fig.4A shows SKR or secret key rate (= success rate of sending quantum information or photons ) drastically decreased and became zero over just 120km.
This extremely unstable quantum information over short distance can Not be used for practical.
↑ In this continuous variable quantum key distribution, quantum information is encoded in (classical) light wave phase ( q base = 0o = 0, 180o = 1, p base = 90o = 0, 270o = 1, ← receiver should choose one of q or p bases and detect its light phase or bit ), which can be detected by light interference in the detector called "homodyne" ( this p.2-A, this p.2 ). ← No photon particle was involved.
Even if receivers managed to get a small fraction of information or fragile photons, irrelevant light or thermal noises caused (quantum key) information errors, which could Not be used as reliable quantum key or ways of sending passwords.
So senders and receivers had to correct information errors by communicating through ordinary classical network called "reconciliation ( this p.2-right-5th-paragraph )", which means quantum key distribution through "quantum network" is meaningless after all (= quantum information or key itself is useless due to its a lot of errors, classical method is necessary after all, this abstract ).
↑ Relying on classical communication for correcting quantum key errors contradicts their original purpose or claim that quantum key distribution should be very secure due to "quantum communication" ( this-middle~lower ).
↑ This classical post-correction of quantum key errors reduced the amount of quantum key information to 0.92 (= reconciliation efficiency β ) × ( 1-0.59(= frame error rate FER ) ) = 50% ( this p.3-(3), p.4-Table.1 ), which means quantum key error rate (= after receiving information ) is more than 50%, which can Not be used as reliable quantum key.
↑ Because more than 50% of quantum key received is wrong and erroneous in addition to massive loss of fragile quantum information or photons in fibers.
As a result, the massive photon (= information ) loss makes practical quantum communication impossible, and the fact that classical communication is necessary for correcting quantum information errors means quantum key distribution itself is meaningless and unnecessary.
The 1st, 3-4th, 12th, 14th, 18th paragraphs of this hyped news say
"Researchers have produced, stored, and retrieved quantum information for the first time, a critical step in quantum networking."
"However, this development is being held up because quantum information can be lost when transmitted over long distances (= quantum network is impractical )."
"To do this requires a means to store the quantum information and retrieve it again: that is, a quantum memory device"
"but both generating these photons on demand and having a compatible quantum memory in which to store them eluded researchers for a long time (= still No practical quantum memory )"
"A 'quantum dot' produced (non-entangled) photons, which were then passed to a quantum memory system that stored the photons within a cloud of rubidium atoms. (= false, this research's so-called quantum memory using rubidium Rb atomic excited energy states could store the absorbed photon or weak light for only extremely short, less than 1 ns, and lost about 90% photons, which is Not a memory at all, this p.3-right-3rd-paragraph says the storage time of only 800 ps, memory efficiency is only 12.9 % = 87.1 % photon loss )."
"The team will (= which means "still useless" ) now look to improve the system, including making sure all the photons are produced at the same wavelength, improving how long the photons can be stored, and making the whole system smaller."
This research just sent weak laser (or fictional photons ) light with telecom wavelength to the so-called quantum memory (= Not a real memory ) consisting of Rb atoms whose excited states could absorb or retain the light or photon information for only extremely-short time (= only 800 ps ~ 1ns ), losing almost all those absorbed photons with extremely-high error rates (= 87% of photons or information was lost inside this unstable atomic memory ), far from a practical memory.
↑ This research paper ↓
p.1-abstract says a total memory efficiency (= ratio of the output photons from memory to the input photons, this p.2-3rd-paragraph ) was only 12.9 %, which means 87.1% of the input photons or light information was miserably lost when entering the quantum memory just one time, completely useless memory.
p.2-left-2nd-paragraph says "To our knowledge, this is the first demonstration of storage and active retrieval of light from a QD (= quantum dot ) single-photon source in an atomic quantum memory (= even this impractical quantum memory with high photon loss rate has not been achieved so far, so quantum technology has been already deadend )"
p.2-Fig.1A,C shows the quantum memory consists of rubidium (= Rb ) atoms whose excited states (= e ↔ s ) were used for absorbing or storing a photon or light for only extremely short time.
p.3-Fig.2C-last says storage time is only 800 ps (= ultrashort ), which is Not a practical memory storing information long enough at all.
p.3-right-3rd-paragraph says "we see absorption of the photons into the memory. Active retrieval of the light is observed at the storage time of (only) 800 ps (= too short to call it "store" )... total memory efficiency is only η = 12.9% (= 87.1% photons or light information were lost in this impractically-unstable quantum memory ) "
p.5-left-QD single-photon source used just weak laser light (= there is No such thing as a photon particle ).
Quantum mechanics ridiculously forbids amplifying and copying the lost photons or light information ( this 19th-paragraph ), so this impractical quantum memory that can store information for only extremely- short time (= only 800ps ) with massive photon loss is irreparable, hopeless forever, except for journals' pseudo-science.
The 2nd, 4th, 7-8th, 10th, 14th paragraphs of this hyped news say
"That's exactly what Harvard physicists have done, using existing Boston-area telecommunication fiber, in a demonstration of the world's longest fiber distance between two quantum memory nodes (= actually No memory appeared in this research ) to date... carrying a signal encoded.. by perfectly secure, individual particles of light (= false, they just used weak laser light, Not a photon particle )."
"The Harvard team established the practical makings of the first quantum internet (= hype ) by entangling two quantum memory nodes separated by optical fiber link deployed over a roughly 22-mile (= just 35 km ) loop (= No internet. This research just sent only one fragile weak light or a photon per 2 hours with a lot of errors, far from internet. this p.11-lower-Table.S6-35km-deployed-loop's success rate was only 0.10 mHz = sent only one photon bit per 10000 seconds = only one bit 0 or 1 information sent in 2 hours, which is far too slow to communicate )"
"The silicon-vacancy center contains two qubits, or bits of quantum information: one in the form of an electron spin (= false, an electron is Not spinning ) used for communication, and the other in a longer-lived nuclear spin used as a memory qubit to store entanglement (= hype, this nuclear magnetic storage time is only 2 seconds, too short-lived, Not a memory at all, this p.4-left-last-paragraph )"
"Both spins are fully controllable with microwave pulses. These diamond devices—just a few millimeters square—are housed inside dilution refrigeration units that reach temperatures of -459°F (= impractically-low temperature )."
"A quantum network cannot use standard optical-fiber signal repeaters because copying of arbitrary quantum information is impossible—making the information secure (= Not practically-secure, they use just fragile weak classical light which is broken by eavesdropper, which can be detected, but the fragile light or photons are easily lost ), but also very hard to transport over long distances (= impractical network )."
"Showing that quantum network nodes can be entangled (= entanglement sends nothing, so useless ) in the real-world environment of a very busy urban area, is an important step towards practical networking between quantum computers (= meaning 'still impractical', still infinite steps left to go for their unrealistic goal )"
↑ This research just sent fragile weak light or a photon (= each photon state bit 0 or 1 was linked with the silicon vacancy's two different energy states, = Not entanglement ) over 35km only one time per 2 hours (= due to massive photon loss, the success rate of sending photons was so low that the receiver had to wait for 2 hours to get only one photon 0 or 1 bit ) with high error rate, far from practical internet.
↑ This research paper ↓
p.2-left-2nd-paragraph (and Fig.1b) says "Under an externally applied magnetic field, Zeeman sublevels define the electronic spin qubit states,.. (= only magnetic field instead of spin was detectable ). Microwave pulses are used to drive the electronic spin-flipping transitions, whereas radio-frequency pulses drive the nuclear spin-flipping transitions (= they just controlled different energy states of silicon vacancy center or SiV by light wave, fictional spin itself was unobservable )"
".. results in an electron-spin-dependent cavity reflectance, which contains a sequence of rapid microwave gates generating entanglement between the electron spin of the SiV and the photonic qubits (= lights emitted from different energy levels related to different magnetic or fictional spin states were reflected differently by cavity mirrors, which they called entanglement that has nothing to do with superluminal spooky link )"
p.2-right-1st-paragraph says "We first use a e-γ gate to generate an entangled Bell state between electron spin ↓, ↑ of node A and an incoming time-bin photonic qubit ∣e⟩,∣l⟩. Here, ∣e⟩ and ∣l⟩ describe the presence of a photon in the early and late time bins of the photonic qubit."
↑ They tried to connect two atomic A,B fictional spin-down (or spin-up ) states (= spin itself was unseen, they just used multiple different energy levels ) with the early-arriving (or late-arriving ) light pulse or photon by using cavity mirror's reflectance difference, which they called entanglement, Not spooky action (= early-arriving light or photon was emitted from one specific energy state )
p.3-Fig.2-a,c shows the success rate of sending photons over only 20m from A to B was just 103 mHz (= 1 Hz = only one time or one photon 0 or 1 bit information sent per second, too slow to send information ), and its error rate of the sent photons is more than 40% (= fidelity is less than 0.6 ), which is a completely useless network.
↑ Due to massive photon loss (= low efficiency ), the actual success probability of sending weak lights or photons over 20m was only 5.0 × 10-5 ( this p.9-Table S3. ) which means about 99.995% of the sent photon information was lost, and even the detected photons showed 40% error rates, which can Not be used as a practical internet or communication at all.
p.4-right-2nd-paragraph says "After using error detection by discarding measurements in which the electronic flag qubits are measured in the |↑e⟩ state, the Bell-state fidelity is 0.77, which is an improvement from the directly measured value of F (= fidelity ) = 0.64 without error detection (= even after artificially discarding some erroneous photons, its error rate was still 23% = fidelity was 0.77, which was completely impractical. = error correction was impossible, all they could do was discarding inconvenient photons post-selectively ).
This p.11-lower-Table S6 shows the success rate of sending fragile photons over the 35km was only 0.1 ~ 0.2 mHz (= millihertz ), which means only one photon per 10000 seconds (= only one photon bit pulse was sent per 2~3 hours ) could be sent over 35km due to massive photon loss (= too slow to send information or do internet ), and even the detected photons showed the high error rate of about 30%. ← unreliable, impractical quantum network
So quantum internet or communication trying to use very fragile photons or weak light as information (= which cannot be copied or amplified due to stupid quantum mechanical rule ) is just a joke, impractical with extremely low success rate (= sending only one photon bit information per several hours with a lot of errors, quantum network or internet is hopeless, deadend ).
↑ This kind of impractical mainstream science intended only for publishing papers in academic journals enables universities to keep skyrocketing tuition limitlessly.
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