(Fig.1) Quantum memory is impractical, losing too many photons or quantum information
The 7th paragraphs of this (4/17/2025) say
"Conversely, quantum memory can only store data for about 100 milliseconds (ms)." ← too short to be a practical memory.
This-p.2-left-2nd-paragraph (5/10/2025) says
"repeaters also require high-performance
quantum memories which, despite years of impressive
progress, are still significant technological bottleneck for
practical implementations"
The 14th, 18th paragraphs of this hyped news (4/16/2024) about (still-impractical) quantum memory say
"A 'quantum dot' produced (non-entangled) photons (= just weak light ), which were then passed to a quantum memory system that stored the photons within a cloud of rubidium atoms."
"The team will (= still do nothing ) now look to improve the system,... improving how long the photons can be stored (= today's impractical quantum memory can retain informaion for only too short time )"
↑ This research paper ↓
p.1-abstract says "We store single photons from an indium arsenide quantum dot in a high-bandwidth rubidium vapor–based quantum memory, with a total internal memory efficiency of 12.9 % (= losing 88.1% of all photons or stored information )."
This p.2-Efficiency (η) says
"The memory efficiency is ratio of probability of detecting the output photon
to that of the input photon ( this p.2-right-last )"
↑ This means even this recent quantum memory (= rubidium atom storing input photon quantum information as excited energy ) lost 87% of all the input photons or quantum inofrmation (= memory efficienty is just about 13% ).
So today's quantum memories losing almost all stored quantum information or photons with extremely low stroing efficienty ( this p.4-left-results. Their storing time is also impractically too short, only 800ps, this-p.3-right-3rd-paragraph ) is completely useless (forever).
The 5th, 2nd-last paragraphs of this hyped news (7/7/2025) say
"demonstrated the heralded storage of photons in a Rydberg superatom (i.e., a cloud of atoms that behave as an individual quantum system under certain conditions = used as impractical quantum memory )."
"In the future (= still useless ), their proposed methods could contribute to the advancement and up-scaling of quantum networks."
↑ This research paper's p.2-right-1st-paragraph says
"we reach an overall storage and read-out efficiency of
ηsr = 16.4% (= 83.6% information was lost ). After storing for about 670 ns (= impractically-short time memory )"
↑ Even this recent quantum memory consisting of atomic clouds lost 83.6% of all information (= absorbed light or photons ) due to low storage efficiency ( this-p.2-efficienty ).
↑ And this impractical atomic quantum memory could store photons or information for only very short time of 670ns, which can Not be used as a practical memory.
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