Wednesday, August 11, 2010

Autonomous quantum error correction technique proposed for quantum memories

Autonomous quantum error correction technique proposed for quantum memories
I just know I am going to need to read this more than 3 times.

The article proposes a solution to error correction in quantum computing cases, by what looks like a tri-state entanglement ... um no thats not it ...

Quote: (format and emphasis are mine)

In general, it’s much more difficult to design QEC methods than it is to design classical error correction methods because in classical methods, bits can simply be copied for redundancy. However, qubits cannot be copied in the same way due to the non-cloning theorem. Yet physicists can get around this limitation in a few ways, such as by encoding a single “logical” qubit (representing the information carried) in the entangled state of three “physical” qubits using a technique called the bit-flip code.

The new autonomous QEC technique is based on the bit-flip code and another similar strategy called the phase-flip code, and can protect the stored information against independent unwanted flips to any, but not more than one, of the physical qubits.

Whereas previous QEC approaches usually involved discrete restoration steps, the new approach involves a continuous syndrome readout to diagnose and correct errors. In this approach, each physical qubit is strongly coupled to its own optical cavity. If an error occurs so that one of the physical qubits has its state flipped, two feedback signals are sent to the qubit to flip it back and correct the error.

The system is autonomous in that probe signals are continuously providing feedback to the qubits: less than two feedback signals in the case of no errors, and two feedback signals in the case of an error.

A diagram of the proposed quantum memory with autonomous quantum error control (QEC). Image credit: Kerckhoff, et al. (c)2010 APS.

Random Thoughts:

This is at once simple and elegant and fiendishly complex.
(and and and and is quite OK here :)

How would this scale beyond single qubit protection ?
(is that even a need ?)

There are very nice almost analogue computing ideas (HAL style) with the "continuous" streaming nature of the feedback and concurrent ternary states.

Mind you monitoring or debugging ... what are the implications of major damage or .. of course there are predictive algorithms about for extra assurances ... downstream comparisons etc.

Pretty cool guys. Way beyond me.
hmm tempted to use the idea in a network script I was working on back a bit ...
(not because it would be more efficient just because it a cool idea)
It would solve a "tri state" issue I have been bulldozing..

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