News & Analysis
Solid-state quantum memory unveiled
R Colin Johnson
1/14/2011 12:53 PM EST
PORTLAND, Ore.—Broadband quantum networks inched closer to reality recently when researchers demonstrated the ability to transfer quantum-bits (qubits) from entangled photons to solid-state crystalline memory devices. Using a super-cooled crystal the researchers were able to demonstrate the reversible transfer of entangled qubits from a quantum network waveguide to the solid-state memory and back again.
Researchers at the University of Calgary (Canada) collaborated with the University of Paderborn (Germany) in the reversible transfer of photon-photon entanglement into entanglement between a photon and the solid-state excitation of atoms. The rare-earth (thulium) doped lithium niobate waveguide made use of the photon-echo quantum memory protocol. Separately, another research group at the University of Geneva (Switzerland) demonstrated a similar capability over a 50-meter fiber optical link, paving the way for quantum repeaters that could extend the ultra-secure communications of a quantum network to any distance.
The University of Calgary team demonstrated that their lithium niobate waveguides, which are already widely used for fiber optic communications, can handle signals from five megahertz to five gigahertz, with a memory retention time of seven nanoseconds. Its broadband quantum memory used off-the-shelf lithium-niobate crystals which needed to be supercooled to minus 270 degrees Celsius. Next, the group plans to create a real-time read-write channel using teleportation to transfer the qubits into and out-of its solid-state memory.
"We have already demonstrated entanglement between a photon and the atoms of the crystal. Our next step will be to use interactions with a third photon to teleport its state into our solid-state memory by virtue of that entanglement," said University of Calgary professor Wolfgang Tittel at the Institute for Quantum Information Science. "This teleportation step will enable future quantum networks that provide ultra-secure long-distance communications."
For the future, besides perfecting teleportation as a means of transferring qubits to and from its quantum memories, the researchers are also planning to extend the memory retention time from seven nanoseconds toward a goal of one second—a necessary condition for using repeaters to create large quantum networks.
Researchers at the University of Calgary (Canada) collaborated with the University of Paderborn (Germany) in the reversible transfer of photon-photon entanglement into entanglement between a photon and the solid-state excitation of atoms. The rare-earth (thulium) doped lithium niobate waveguide made use of the photon-echo quantum memory protocol. Separately, another research group at the University of Geneva (Switzerland) demonstrated a similar capability over a 50-meter fiber optical link, paving the way for quantum repeaters that could extend the ultra-secure communications of a quantum network to any distance.
Quantum networks will allow sending information without being afraid of somebody listening in. Photo credit: Riley Brandt
The University of Calgary team demonstrated that their lithium niobate waveguides, which are already widely used for fiber optic communications, can handle signals from five megahertz to five gigahertz, with a memory retention time of seven nanoseconds. Its broadband quantum memory used off-the-shelf lithium-niobate crystals which needed to be supercooled to minus 270 degrees Celsius. Next, the group plans to create a real-time read-write channel using teleportation to transfer the qubits into and out-of its solid-state memory.
"We have already demonstrated entanglement between a photon and the atoms of the crystal. Our next step will be to use interactions with a third photon to teleport its state into our solid-state memory by virtue of that entanglement," said University of Calgary professor Wolfgang Tittel at the Institute for Quantum Information Science. "This teleportation step will enable future quantum networks that provide ultra-secure long-distance communications."For the future, besides perfecting teleportation as a means of transferring qubits to and from its quantum memories, the researchers are also planning to extend the memory retention time from seven nanoseconds toward a goal of one second—a necessary condition for using repeaters to create large quantum networks.
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Frank Eory
1/14/2011 3:48 PM EST
I guess Heisenberg's uncertainty principle is disproven? If not, how can a quantum memory work? It seems like the mere act of reading a quantum memory value would also cause the value to change.
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Dainivtone
1/15/2011 6:51 AM EST
Solid state shrinkage is the reduction of size for a material that already is solid. Railway tracks get smaller when it's cold.
http://www.healthproductreviewers.com/lifecell-skin-cream-review.html
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prabhakar_deosthali
1/17/2011 1:00 AM EST
I could not understand how this new quantum memory technology will make the future networks SECURE. Most of the other technologies the hackers will go one step ahead to break the security of even these networks. Can somebody enlighten me on this?
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entity279
1/17/2011 3:13 AM EST
Think about it this simple way: if you have some bits of your key entangled with the data you need secured, then the hacker with the different key will just get a different (meaningless) data without being able to tell that
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pixies
1/17/2011 2:26 PM EST
Now I understand why in so many sic-fi movies the computers were made of crystals (Superman and Star Gate, for examples.)
Joking aside, quantum entanglement hold so much more potential than just encrypt communications. It is a pity to see physicists have to justify their research with a practical applications.
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iniewski
1/18/2011 11:49 AM EST
To @pixies: Why would say it is a pity to justify the research? Do you really expect taxpayers to pay for research which serves no practical applications at some point? Kris
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Lionlair
1/21/2011 7:55 PM EST
Pure research is needed to create new abilities. When research is dependent upon the final product - then much of what we know would have never been discovered. When forced under product needs, only products along that line are developed or nothing at all since the concept never sees the light of day.
Martin
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iniewski
1/21/2011 8:01 PM EST
Sure, pure research is needed, I think everybody would agree with that statement...but how much of the pure research gets funded through taxpayers money is a real issue. And how do we select what is worth funding or what is not. Hopefully neither @pixeies or @lionlair are not suggesting that every scientist researches whatever he/she feels like it? (I end up paying for it)...Kris
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