GOOGLE QUANTUM ERROR CORRECTION CODE
The team started implementing the linear code with 5 physical qubits and then gradually scaled it up to 21. In their paper in Nature, the Google researchers describe how they trialed two different codes: one that created a long chain of alternating data qubits and measure qubits and another that created a 2D lattice of the two different kinds. But now Google has demonstrated the approach in its 52-qubit Sycamore quantum processor and shown it should scale up to help build the fault-tolerant quantum computers of the future.Ĭreating a logical qubit relies on what is known as a stabilizer code, which carries out the necessary operations to link together the various physical qubits and periodically check for errors. While these ideas are not new, implementing them has so far proved elusive, and there were still some question marks about how effective the scheme could be. To detect these errors, the so-called “data qubits” that encode the superposition are also entangled with others known as “measure qubits.” By measuring these qubits it’s possible to work out if the adjacent data qubits have experienced an error, what kind of error it is, and in theory correct it, all without actually reading their state and disturbing the logical qubit’s superposition.
In theory, this makes it possible to detect and correct errors in individual physical qubits without the overall value of the logical qubit becoming corrupted. This can be used to lump together many qubits to create one “logical qubit” that encodes a single superposition. To get a round this problem, scientists have turned to another quantum phenomenon called entanglement, which intrinsically links the state of two or more qubits. Any attempt to measure the qubit causes this state to collapse to a 0 or 1, derailing whatever calculation it was involved in. Unlike normal binary bits, the qubits at the heart of a quantum computer can exist in a state known as superposition, where their value can be 0 and 1 simultaneously. The problem is that the most obvious way of checking for errors is out of bounds for a quantum computer. This can introduce errors into calculations, and it’s widely accepted that error correction will need to be built into these devices before they’re able to carry out any serious work. The power of quantum computers comes from their ability to manipulate exotic quantum states, but these states are very fragile and easily perturbed by sources of noise, like heat or electromagnetic fields.
GOOGLE QUANTUM ERROR CORRECTION HOW TO
Now, Google has provided an experimental demonstration of how to correct this problem and scale it up for much larger devices. One of the biggest barriers standing in the way of useful quantum computers is how error-prone today’s devices are.
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