Photon quantum computer is impractical forever due to photon loss.

Photons are too easily lost to become quantum computers.

Useless photon qubits due to photon loss.

Just detecting 4 photon qubits is impractical.  ← Photon quantum computers are useless forever.

Room-temperature photon quantum computer is a lie.

The 7th paragraph of this or this-site says  -- Fake room temperature photon
"Current hype around photonic is that photon qubits do not need to be cooled,...
However, the components used to manipulate and detect photons, such as waveguides, beam splitters, and detectors, often rely on materials that require cryogenic temperatures."

Actually, even 4 photon qubits are almost impossible.

Even now in 2026, just detecting 4 photons (= 4 qubits ) is almost impossible due to severe photon loss, which cannot make quantum computers.

Due to massive loss of photons, even 4 photon qubits are almost impossible to make.

This recent hopeless photon quantum computer (7/2026) ↓

p.1-abstract says  -- Useless 4 photon qubits
"Here, we demonstrate.. up to four qubits. We achieve fidelities of FStar = (83.5 ± 1.8) % and FLin = (75.6 ± 1.1) % for four-photon"  ← Just 4 photon qubits caused high error rates (= 100% - fidelity ) of 25%, completely impractical.

p.3-left-Results say  -- Too slow due to photon loss
" We obtain a direct fidelity estimation.. at rates of 12.1 mHz and 13.3 mHz (= too slow ! )"

↑ Due to massive loss of photons (= weak light ), they could barely detect 4 photons at the very low rate of just 12 mHz or 12milliHerz (= measure photons just 12 times per 1000 seconds ), which is too slow and impractical.

Just detecting 4 photon qubits is impractical and No quantum computation.

Creating just 4 photon qubits even without 2-qubit gate operation is almost impossible due to severe photon loss.  ← Photon quantum computers are impossible forever.

This or this or this news on another overhyped hopeless photon quantum computer (8/2026) ↓

6th-paragraph says  -- 2 photon qubit gate is impossible
"Two photons, by contrast, pass right through each other. Creating a two-qubit entangling gate on a photonic chip requires either a lossy nonlinear medium or a probabilistic linear-optical scheme that succeeds only a fraction of the time."  ← Two-photon-qubit gate is impossible.

7th-paragraph says  -- Detecting 16 photon qubits is impossible
"If you want to entangle two photons, you might succeed on the second or third try. If you want to simultaneously entangle sixteen photons into a single GHZ state (= making all qubits 0 or 1 states ), the probability of all sixteen arriving at the right place in the right state at the right time drops to essentially zero."

"This is why the prior on-chip record was four photons, and why nearly all photonic chip demonstrations to date work with two-photon or at most four-photon states."  ← Just 4 useless photon qubits are the maximum

9th-paragraph says
"A photon traveling through a silicon waveguide chip can be routed through many distinct waveguide paths. Each unique path is a distinct quantum basis state. A photon in a superposition of N distinct paths represents a qudit — a quantum system with N distinct levels, carrying log₂(N) qubits of quantum information."

10th-paragraph says  -- 4 photons = 16 qubits ?
"Four photons then encode 16 qubits — without requiring those photons to interact with each other."

14th-paragraph says  -- Detecting just 4 photons is difficult
"A four-fold coincidence rate of just 12.1 millihertz"  ← Detecting 4 photons coincidentally at the very low rate = only 12 times per 1000 seconds due to severe photon loss.

20th-paragraph says  -- No error correction
"through post-selected operations that can be tried multiple times until they succeed"  ← Just discarding erroneous results without error correction

6th-last-paragraph says  -- Fake 16 qubits
"High-dimensional encoding mitigates the photon-number problem (fewer photons needed for the same qubit count) but does not directly address the loss-per-photon problem. A photon carrying four qubits is still one photon that can be lost — and losing it means losing four qubits at once rather than one."

↑ So even now in 2026, researchers could barely detect only 4 photons (= just 4 qubits,  16 qubits are fake ) at the very low rate, which is impractical forever.

Today's photon quantum computer is useless with only less than 12 qubits (= one qubit takes only 0 or 1 value ), far from the hyped million qubits.

(Fig.M)  ↓ PsiQuantum's million photon qubits is overhyped fake news.

PsiQuantum's million photon-qubit quantum computer is a lie to deceive taxpayers.

The 1st, 6th paragraphs of this or this-(2025) say  -- Million qubit lie
"PsiQuantum has announced that it has raised $1 billion of Series E funding to further its goal of building fault-tolerant quantum computers at the scale of one million qubits."  ← lie, impossible

"Only building the real thing - million-qubit-scale, fault-tolerant machines - will unlock the promise of quantum computing,"  ← Million qubits are necessary for a useful quantum computer, which is impossible to realize forever.

Photon quantum computer is impractical forever

Even the latest photon quantum computer has less than 12 qubits ( PsiQuantum has only 4 photon qubits ), far from millions of qubits required for a useful computer.

↑ Even today's largest (impractical) photon quantum computer has only 12 qubits in Xanadu ( this or this-2nd-paragraph in 2025,  this-insider brief ), which is far from millions of qubits.

This-abstract-lower (2025) says  -- Only 4-qubits
"For 4-qubit states, our circuits achieve success probabilities of 2.053×10⁻³ "  ← Just detecting 4-photon-qubits is too difficult with very low success rate of only 0.002053 due to massive photon loss.

↑ Xanadu's latest research paper in 2025 ( this or this-p.63-Figure S28 ) says probability of detecting just 5-photons (= 5 qubits ) is extremely low = only 0.000047.

Photon qubit numbers of fake quantum advantage, which just randomly detected photons without quantum computation nor error correction, are Not real qubit numbers.

(Fig.2)  A photon or very weak light is too easily lost. which makes it impossible to scale up photon or optical quantum computer ↓

Photon qubit is just weak classical light wave split by a beam splitter.

A photon or weak light going to the upper (= 0 ) or lower (= 1 ) path at a beamsplitter is used as a photon qubit.

Photon quantum computer tries to use a fictional photon particle or weak light as a quantum bit or qubit.

Each photon or light's polarization is often used as a qubit state (= vertically-polarized light is used as a qubit's 0 state,  horizontally-polarized light is used as a qubit's 1 state ).

In a photon quantum computer (= still Not a computer ), when each photon or weak light splits at a beam splitter (= BS ) into the upper path (= upper waveguide ) or the lower path, these paths or waveguides are used as a photon qubit's two states (= each qubit can take 0 or 1,  a photon in the upper path means a qubit's 0 state,  a photon in the lower path means a qubit's 1 state,  this p.1-Fig.1,  this-Figure 1,  this or this-2nd-paragraph ).

When a photon (= just weak divisible classical light wave ) magically splits into both upper and lower paths at a beam splitter, it is treated as quantum superposition where each photon can be both in the upper and lower paths simultaneously using fictional parallel worlds ( this p.35-Fig.3.5 ).

A photon can split into two paths 0 and 1 at a beam-splitter using (fictional) quantum superposition or parallel universes !?  ← nonsense

↑ Of course, this quantum superposition or parallel worlds are just fiction.
A photon is just a divisible weak light that can realistically split at a beam splitter.

This or this-9th, 11th paragraphs say  -- Unreal photon superposition

"Then, photons are moving inside a waveguide in one direction (could be compared to plumbing pipes where you send water in). Each waveguide is called a mode, the unit of light in each mode is used to represent a qubit, two modes and one photon can encode 1 qubit. Imagine the modes as two parallel lines where the photon can be either on the upper line or the bottom line. At this point we can agree that having a photon on the upper waveguide corresponds to qubit in state |0> and the lower waveguide corresponds to qubit in state |1>, and this is the general idea that defines our qubits. We call it dual-rail encoding"

"For instance, assume we have |0> how do we end up in a quantum superposition ? ..
Once the single photon passes into a beam splitter it will move randomly in the upper or lower mode with a 50–50 chance. Furthermore, we might need different probabilities for example 30–70% or 40–60%, in that case we must have more sophisticated beam splitters using phase shifters (also called unbalanced beam splitters)."

(Fig.3)  Photon qubits (= just weak classical light ) are too fragile, lost too easily to be a practical quantum computer ↓

Massive photon loss makes it impossible to realize quantum computers forever.

The problem is a fragile photon or weak light so easily gets lost that quantum computers using such unstable photons as qubits are impractical forever ( this or this-4th-paragraph,  this or this-p.5-right-4.4,  this or this-p.1-left-2nd-paragraph ).

This-middle Photonic networks say  -- Photon loss error

"Unlike with other qubit technologies, two-qubit gates in photonic networks are probabilistic (= random, causing errors ), not deterministic."

"..However, fidelity at scale is a significant hurdle for photonic networks. The largest source of error for photonic networks is photon loss during computations."

This or this-Challenges of Photonic Quantum Processors say  -- Photon loss

"Losses: Photons are easily lost, limiting the performance of photonic quantum processors.
Control: It is difficult to control photons' behaviour, making it challenging to perform complex quantum operations.

Error correction: Quantum computers are susceptible to errors, which means that error correction techniques need to be developed to ensure the accuracy of calculations."

This or this-2nd-paragraph says "One of the main challenges in photonic quantum computing is the loss of photons"

Photon are too unstable, too slow, unable to do gate operation.

This-p.1-right-2nd-paragraph says  -- Photon loss

"The remaining criteria are harder to satisfy because photons don’t easily interact, making deterministic two-qubit gates a challenge (= still useless, because changing a qubit based on another qubit state = two-qubit gate operation needed for computation is impossible ). Among the additional technical considerations is photon loss,.."

".. And although photons are always flying, computing and networking tasks may need them to be delayed or stored (= usually very long bulky light cables to confine the always-flying photons or light are needed ), so an extra device—an optical quantum memory (= still impractical ) —may sometimes be needed."

↑ The impractical photon quantum computer with easily-lost photons ( this p.1-right-1st-paragraph ) motivated physicists to focus only on detecting meaningless random photons (= just divisible weak classical lights ) in fake quantum advantage.

Due to the significant photon loss, the speed of detecting (easily-lost) photon qubits is much much slower (= only 10 Hz = only 10 photon qubits can be detected per second, impractically slow ) than other ( superconducting ) qubits (= 1.4 MHz = 1400000 Hz ), as shown in this or this-Platform's table~.

Even a single logic gate of by such a fragile photon has Not been built, a photon quantum computer is far more impossible.

(Fig.4)   Photon quantum computer cannot manipulate qubits nor calculate anything by (impractical) logic gates. ↓

Logic gates of photon quantum computers are impossible, too error-prone.

Even connecting two photons qubits by two-qubit gate operation is impossible, which means photon quantum computers are impractical forever.

A real computer needs logic gates which change the state of a bit (or qubit ) 0 ↔ 1 by other bits (or qubits ) for calculation.
But a photon quantum computer still cannot realize even one two-qubit logic gate (= two-qubit gate operation means "change one qubit state 0 ↔ 1 based on another qubit state" ) consisting of (classical) beam splitters (= BS ).

This p.3-A universal set of quantum gates say  -- No two-qubit gate
"arbitrary single-qubit operations can be expressed as combinations of beamsplitters and phase-shifters—an optical interferometer (= for changing photon qubit state or path )...

The implementation of two-qubit gates is a challenge for photons. The fact that photons do not interact also means that it is difficult for the operation on one photon depend on the state of the other."

This p.1-introduction-1st-paragraph says  -- No photon qubit gate
"in photonic systems, weak photon-photon interaction renders two-qubit gates difficult (= photon quantum computers cannot calculate anything by conducting gate operation )"

2-photon-qubit gate operation is impossible forever.

Each 2-photon-qubit gate operation's error rate is too high = 75%, which cannot compute anything.

This-paper on the hopeless 2-photon-qubit gate (8/2026) ↓

p.1-left-1st-paragraph says  -- Impractical photon quantum computers
"However, in photonic quantum information processing, a fundamental challenge persists as the implementation of deterministic multi-photon quantum gates remains elusive due to the weak nonlinear interactions between individual photons. This limitation results in inherently probabilistic gate operations, significantly hindering the scalability of optical quantum computing system"

p.1-left-last~right-1st-paragraph says  -- 75% error rate
"Nowadays, experimental implementations of CNOT gates (= 2-qubit gate ) in multiphoton systems can generally be divided into three categories"

"The second category improves the success probability to 1/4 by employing an additional pair of maximally entangled photons, and this approach represents the highest success probability to date"

"Beyond these basic gates, research has also extended to more complex multiple-photon gates like Toffoli and Fredkin gates, though these typically exhibit lower success probabilities."

↑ Each 2-photon-qubit gate operation's success rate is only about 1/4 (= 25% ), which 75% high error rate keeps photon quantum computers impractical forever. ↓

Each photon operation causes 76% error rate, which cannot be used for quantum computers.

Error rate of a photon quantum computer's logic gate is still high = more than 76%, which is useless.

This or this-recent paper on (useless) photon's two-qubit logic gate (= one photon's state influences the other photon's state ) ↓

p.1-Abstract says  -- Too high error rate
"The experimentally achieved efficiency in an optical controlled NOT (CNOT) gate reached approximately 11% in 2003 and has seen no increase since (= photon's two-qubit gate operation error rate is impractically-high = 89% = 100% - 11% efficiency )..
We demonstrate a CNOT gate between two optical photons with an average efficiency of 41.7% (= still error rate is impractically high = about 60% )"

↑ Efficiency is the success rate or the probability that a desirable photon was detected by a photodetector ( this or this-p.1-3rd-paragraph ).
This success rate (= efficiency) was still very low = only 41.7%, which is useless.

↑ So the error rate (= more than 60% error rate ) of a photon two-qubit gate operation is impractical and far worse than error rates (= 1%) of even other (impractical) superconducting or ion qubits

Photon qubits are far worse than other (impractical) qubits.

Photon quantum computer's error rate (= more than 76% ) is far worse, higher and more impractical than other superconducting or ion qubits' error rate (= 1% = which error rate is also impractically high ).

↑ The same paper ↓

p.2-Fig.1 shows  -- No photon computer
photon's quantum computer's two-qubit logic gate consists of (classical) polarizing beam splitters and mirrors where two lights destructively or constructively interfering determine the final qubit state (= which path photon is detected in the last ).

p.4-left-C. says "The efficiency of the gate is the probability that no photon is lost inside the gate, if one control and one target photon impinge on the gate"

p.9-left-1st-paragraph says  -- 76% error rate
"Multiplying this by the 41.7% average efficiency of the gate, one obtains a 24% probability of detecting a two-photon coincidence per incoming photon pair (= only 24% photons could be detected, which means the remaining 76% photons were lost, or its error rate is extremely high = 76% )."

p.9-left-2nd-paragraph says  -- Massive photon loss
"obtain a naive estimate for the two-photon coincidence rate of 10 s−1 (= only 10 pairs of photons or 10 qubits were detected per second, which is too slow and useless as a computer due to massive photon loss )"

Even detecting 3 ~ 4 photon qubits is impractical, too slow due to massive photon loss.

(Fig.5)  Photon qubits are too easily lost.  ← Detecting multiple photons (= qubits ) simultaneously is unrealistic. ↓

Just 4 photon qubits are hard to make.

Detecting just 3 ~ 4 photons (= qubits ) simultaneously is almost impossible.  ← Photon quantum computer is impossible.

To scale up photon quantum computer, physicists need to simultaneously detect as many photons (= each photon is used as a qubit taking 0 or 1 states ) as possible.

If they cannot simultaneously detect multiple photons or multiple qubits, it means photons or qubits relevant to calculations are lost (= so calculation using the easily-lost photons is impossible ), or irrelevant background photons are mixed.

So increasing success rate of simultaneous detection of multiple photons or qubits is indispensable for scaling up the photon quantum computer.

But the present simultaneous photon detection rate is too bad and too low to scale up a photon quantum computer (= even success rate of detecting only small numbers of 4 ~ 8 photons or qubits is unrealistically low and too bad ).

n-fold coincidence means n different photdetectors detect each photon simultaneously (= 3-fold coincidence means 3 detectors detect 3 photons simultaneously ).  ← Even this is very hard.

Two-coincidence (or three-coincidence ) means 2 photodetectors (or 3 photodetectors ) detect 2 photons (or 3 photons ) simultaneously ( This or this-p.12-Figure 5 ).

This or this-p.2-1.2 and p.3-2.1 say  -- Simultaneous photon detection.
"If n detector events (from different detectors ) happen within a time window of width ∆tw (called "coincidence time window" ), we call that an n-fold coincidence. 3-fold coincidences are also counted as 3"

"Now, we want to look at 2-fold coincidences between detector 1 and 2"

This or this-p.4-left-Discussion says  -- Hard to detect 4 photons
"The four-fold coincidence count in our experiment is about three counts per hour"  ← So they could detect 4 photons simultaneously at extremely-low rate of only 3 times per hour due to massive photon loss, which is completely impractical for quantum communication or internet.

Detecting just 4 photons is very hard.

Success rate of detecting only 4 photons or 4 qubits simultaneously is extremely low = only 0.000000001, which is useless.

The recent research paper ↓

p.4-right-Experimental design says "pumped by a femtosecond ultraviolet laser (390 nm, 76 MHz = 76 × 10⁶ photons or weak light pulses were generated )"

p.5-left-last paragraph says  -- Detecting 4 photons hard
"the final fourfold coincidence rate (= rate of detecting only 4 photons simultaneously ) is about 0.03 Hz (= 1 Hz or Hertz means detecting one photon per second )."

↑ It means only 0.03 photons (= 0.03 simultaneous four-photon detection ) per second were detected (= only 0.03 × 4 = 0.12 photon bits or information per second can be utilized ), which is too few and too slow to use as a computer's memory (qu)bits.

Simultaneous four-photon detection rate was 0.03/76000000 = 0.000000001 = 99.9999999 % error rate due to photons' loss, which is completely impractical.

Success rate of detecting only 6 photons or 6 qubits simultaneously is extremely low = 0.0000000001, which is impractical.

This another recent research paper ↓

p.2-left-2nd~3rd-paragraph says "pulse laser with a repetition rate of ∼76 MHz, the QD emits ∼50 MHz polarized resonance fluorescence single photons at the end of the single-mode fiber (= about 50 MHz or 50 × 10⁶ photons or light pulses were generated from the light or photon source )"

p.5-Fig.4a shows  -- Hard to detect 6 photons
the six-photon coincidence counts (= the total number of detecting 6 photons simultaneously ) were only less than 160 per 23 hours, which counts were too few and too slow to be practical.

↑ the 6-photon simultaneous detection rate was only 160/(50 × 10⁶ × 3600 × 23 ) < 0.0000000001, which is extremely low, and useless.

Photon quantum computer, which can Not detect even 10 photons or 10 qubits, is impractical forever.

Another recent paper ↓

p.1-right-last-paragraph says "That is, by combining a quantum dot (QD)–based photon source, from which we measure single-photon count rates at 17.1 MHz (= 17.1 × 10⁶ photons were estimated to be generated from light source per second )"

p.5-Fig.4c shows  -- 8 photon qubits hard
the coincidence 8 photon count rate drastically decreased to only less than 0.01 Hz (= less than one detection per 100 seconds ) from the original single photon rate of 17.1 MHz (= 17100000 Hz ), which means success probability of detecting 8 prepared photons simultaneously is only 0.01/17100000 = 0.000000001.

↑ Detecting only 8 photons or 8 qubits is too slow (= just 0.01 detections per second ), hence, building just 9 ~ 10 photon qubits is impossible, which is far from a practical quantum computer that will require millions of qubits.

As a result, the probability of detecting multiple photons simultaneously is extremely low and disastrous, which large photon loss makes it impossible to scale up photon's quantum computer forever.

Even the probability of successfully preparing one fragile photon (logical) qubit ( = GKP state ) needed for photon error detection is only less than 1% (= usually < 0.00001 ).  ← Quantum error correction is impossible.

(Fig.6)  Only a few (fragile) photon qubits can be generated per second ?  ← this is too slow and too impractical.

Mixing multiple lights for error detection is useless.

Making a photon's logical qubit (= GKP state mixing multiple lights ) for detecting errors is unrealistic.

"However, a significant challenge lies in generating specialized states like the Gottesman-Kitaev-Preskill (GKP) state (= a photon's logical qubit mixing multiple weak lights or photons, this p.1-abstract ), crucial for error correction and achieving fault tolerance"

"indicating the successful projection of the last mode into a GKP state. Nevertheless, this approach is probabilistic, with a success rate as low as 1% or even lower (= photon error correction needs to create GKP light superposition state, which success rate is only less than 1%, which is useless )"

Even in the latest research in 2025, the success probability of producing this single fragile photon logical qubit (= GKP state ) just mixing multiple weak (classical) lights with different phases ( this quantum state of light ) is only 0.00001 (= 10^-5 = impractically low,  this abstract ) due to severe photon loss (= photon error correction is still impossible ).

↑ Photon quantum computers and their error correction (= correcting photon loss or wrong phase shift ) are impossible, unrealistic forever.

Even one logical photon (GKP) qubit is hard to create.

Probability of generating the photon's GKP state mixing multiple lights for error detection is impractically low, so photon's error correction is impossible forever.

The 4th, 10th paragraphs of this or this-overhyped news (6/4/2025) say
"In this experiment, researchers used a special type of qubits known as Gottesman-Kitaev-Preskill (GKP) states, which allow many photons to encode error-free information "

"The next step, Xanadu said, is to reduce optical loss in its quantum systems ( this-last-paragraph )"  ← still optical or photon's loss cannot be avoided, so useless.

↑ This research paper ↓

p.2- Fig.2-last says  -- Only one qubit
"when the correct detection pattern is observed, herald the production of a GKP qubit state"  ← Xanadu tried to realize just one qubit called GKP (= a single logical photon qubit taking only 0 or 1 value, still Not a quantum computer ).

p.3-left-last says  -- Low success rate
"heralded with 2.9 × 10⁻⁴ success probability (= this success rate is too low and too bad )...  30 Hz (= too slow, only 30 times per second ) success rate with the chosen discarding ratio"

p.6-right says  -- Not room temperature
"The PNR detectors are based on a cryogenic transition edge sensor design operated in a dilution fridge at 14 mK"  ← Not room temperature, contrary to hypes ( this-7th-paragraph ).

The 2nd, 3rd paragraphs of this hyped news (7/14/2025) say
"The system combines quantum light sources and stabilizing electronics using a standard 45-nanometer semiconductor manufacturing process to produce reliable streams of correlated photon pairs (particles of light)—a key resource for emerging quantum technologies. The advance paves the way for mass-producible "quantum light factory"  ← overhyped fake news

"This is a small step (= still unrealized ) on that path"

Bulky impractical photon chip of 9mm size

↑ This research paper ↓

p.9-1st-paragaph says "the photon detection efficiency (PDE). The PDEs of the idler and two signal SNSPD channels,.. to be 63% (= error rate of 37% ), 77%, and 74%"  ← Error rate of detecting each photon (= one qubit 0 or 1 ) is too bad = 30 ~ 40%.

p.11-Fig.1(b) says "the entire 2 mm×9 mm electronic-photonic CMOS chip, which contains 12 photon-pair source blocks"

↑ Very bulky impractical photon chip of 2 × 9 millimeter size emitting only 12 photons (= just 12 quantum bits ).

↑ So this overhyped photon chip is useless (= commercialization is hype, impossible ), far bigger (= ~ 9mm ) and bulkier than today's practical 45nm transistors.

Xanadu with No useful quantum computers can only roughly estimate how much qubits will be needed to calculate some photosensitizer's molecular energy in future with No quantum computation nor quantum mechanical prediction.

Xanadu photon quantum computing company is said to develop quantum computing framework for photodynamic cancer theory, which is fake and useless with No quantum computation..

This or this-hyped Xanadu quantum cancer therapy news ↓

7th-paragraph says  -- Just future estimate, No computation
"Resource estimates, obtained using PennyLane (= classical computing software ), suggest simulating systems with 11-45 spatial orbitals requires 180-350 logical qubits,,, indicate the feasibility of running these algorithms on future (= still unrealized ), realistic fault-tolerant quantum devices."

↑ So this research just vaguely estimated how many (logical) qubits will be needed to calculate some photosensitive molecules (= whether these are used for cancer theory is unclear ) in future with No actual quantum computation.

↑ Actually, still No single errorless logical qubit has been realized, and it is extremely difficult for the useless photon quantum computer to have more than 4 qubits (= one qubit takes only 0 or 1 value ) due to photon loss, so quantum computation for cancer-related molecular energy is impossible. ↓

No quantum computation, No cancer therapy.

This research tried to calculate some molecular energy related to cancer phototherapy by a classical computer based on the useless quantum mechanical unsolvable Schrodinger equation that cannot predict anything, and roughly estimate how many qubits will be needed in future to further calculate its excited energy with No computation.

↑ This paper on Xanadu's fake quantum cancer therapy ↓

p.1-abstract says  -- Just estimation, No computation
"Our resource estimates, obtained with PennyLane, suggest that systems with active spaces ranging from 11 to 45 spatial orbitals can be simulated using 180-350 logical qubits"  ← This research just roughly estimated how many logical qubits will be necessary in future without actual quantum computation

p.3-Table I says  -- No quantum computation
"Resource estimates (= just estimation without actual quantum computation ), obtained with PennyLane (= classical computing software ), for cumulative absorption using the threshold projection algorithm.. evaluated across active spaces of N spatial orbitals for several BODIPYclass photosensitizer molecules"

p.8-left-last-pargraph says  -- No quantum mechanical prediction
"This is a reasonable assumption, given the well-known capability of classical methods such as DMRG (= approximate CI, this-p.13-5th-paragraph ) or selective configuration interaction (= CI )"

↑ Configuration interaction (= CI ) and DMRG is the impractical quantum mechanical variational method just choosing fake trial wavefunction for unsolvable Schrodinger equation that cannot predict anything.

↑ So this research just estimated how many (logical) qubits (= one logical qubit can take only 0 or 1 value ) will be needed in the future in still-non-existent quantum computer to calculate energy of photosensitive molecules (= still No calculation of specific energy in this research ) with the help of a classical computer, which cannot predict anything nor cure cancers due to the impractical quantum mechanical unsolvable Schrodinger equation.