Pushing the speed limits of quantum memory

It feels like quantum computers have barely been invented, and scientists are already testing how extensible the current technology is. A paper published in Nature Photonics this week describes how researchers are beginning to push the bandwidth limits of quantum memory. Using photon pulses and cesium vapor has provided bandwidths on par with broadband connections, rates 100 times those of other quantum memory systems currently being tested. However, the system's efficiency is still very low, and advances will have to be made in other fields before it can be improved.

Since many quantum computing implementations operate on photons, a quantum memory that doesn’t involve converting photons into other media, like electrical pulses, would be ideal. Unfortunately, current photon-based media suffers from problems with storage time, retrieval efficiency, and bandwidth. The paper tackles the last issue, as current quantum systems are limited to a data rate of a few megahertz at most.

To create more bandwidth, scientists used a bunch of atoms instead of one or two. A cloud of hot cesium vapor served as the storage medium. Once the vapor had been prepared in its ground state, scientists sent a "write" pulse into the vapor along with a signal pulse that contained the information to be stored. The vapor converted these two pulses into a collective atomic excitation, called a spin wave. To get the information back out, scientists sent a "read" pulse that converted the spin wave back into a signal that was read by a detector.

With this method, scientists found that the bandwidth of the signals they could process was a bit better than 1GHz. This transmission was actually limited by the output detector, not the signal itself—theoretically, this style of storage should be capable of even larger bandwidths. The system also had excellent coherence, holding up well when subjected to interference.

However, the setup didn’t retain the information that well. While scientists found that they could increase the retention by sending more energetic read and write pulses, the total efficiency of the system topped out at 15 percent: the cesium vapor was able to store 30 percent of the incident signals, and they could only retrieve half of what was stored.

Researchers speculate that the overall efficiency of the process was poor because the signal pulse may not be optimal. Changing any of a number of its attributes, such as the shape and frequency, could lead to much higher storage and retrieval rates. However, shaping pulses with frequencies less than a nanosecond is itself a developing technology.

While the experiment did push a few boundaries, it seemed to hit limits already established by other technologies—limits that will have to be pushed themselves before much more progress can be made. The researchers noted that the applications of this particular kind of storage are broad, and might work with cold gases and solid-state systems in addition to the hot vapor they used. However it will eventually be accomplished, the baton pass from quantum memory conception to development seems to be underway.

Source: ars technica

Comments
Add comment

Your name:
Sign in with:
or
Your comment:


Enter code:

E-mail (not required)
E-mail will not be disclosed to the third party


Last news

 
 
With the head of Samsung Group facing prison time, CEO calls for company to "start anew"
 
Is there a way to turn off the iPhone or iPad that doesn't require a button?
 
Users will be warned that the app is still in development and will be unstable
 
Quick test proves fast charging isn’t as fast as promised
 
Bitcoin shrugs off Chinese regulations and bubble chatter to smash a new record
 
Microsoft moves the controls to the Settings app
 
The Exynos-powered Note8 are capable of capturing videos at 60fps, not just 30fps, but the software on them doesn't allow it
The Samsung Galaxy A5 (2017) Review
The evolution of the successful smartphone, now with a waterproof body and USB Type-C
February 7, 2017 /
Samsung Galaxy TabPro S - a tablet with the Windows-keyboard
The first Windows-tablet with the 12-inch display Super AMOLED
June 7, 2016 /
Keyboards for iOS
Ten iOS keyboards review
July 18, 2015 /
Samsung E1200 Mobile Phone Review
A cheap phone with a good screen
March 8, 2015 / 4
Creative Sound Blaster Z sound card review
Good sound for those who are not satisfied with the onboard solution
September 25, 2014 / 2
Samsung Galaxy Gear: Smartwatch at High Price
The first smartwatch from Samsung - almost a smartphone with a small body
December 19, 2013 /
 
 

News Archive

 
 
SuMoTuWeThFrSa
1234567
891011121314
15161718192021
22232425262728
293031    




Poll

Do you use microSD card with your phone?
or leave your own version in comments (4)