Improved Quantum Error Correction Scheme Developed

[Guest_Jim_*]

Correcting errors is important for the reliable operation of any computing device. For modern computers, we have it down pretty well, but for future quantum computers, the challenge is completely different. Researchers at MIT though have managed to overcome one significant aspect of the challenge, by breaking the limit others suffer.

Quantum computers get their name and extraordinary power from quantum mechanics, which presents a special challenge. In classical mechanics, measuring a system tends not to change it, but in a quantum mechanical system can change it, as demonstrated by Schrodinger's Cat. Because of this there was a time when researchers believed it would be impossible to correct errors in a quantum computer, because measuring the values of qubits would cause them to collapse, defeating the purpose. Despite those concerns, error correction systems have been developed that do not actually measure the qubits' value, but their relationship to others. All of these systems are limited to only working on a square root of the total number of qubits (so you could only correct eight qubits in a 64-qubit computer). The new MIT method breaks that limit by using a special qubit bank and time. As the qubits are manipulated in the computer and take on new states, a bank of qubits is assigned to each state. By analyzing relationships within the banks, it is possible to determine where an error occurred and to fix it.

Ironically, this approach does not prevent errors and could even introduce them, but what errors there are must obey certain rules, which is why they can be corrected later. This approach allows for an arbitrary fraction of the qubits in a quantum computer to be checked for errors, and thus breaks the square root limit. Now the question is how much redundancy is needed amongst the qubit banks, and if fewer can be used, simplifying the system.

Source: MIT

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