Abstract
The use of analog classical systems for computation is generally thought to be a difficult proposition due to the susceptibility of these devices to noise and the lack of a clear framework for achieving fault-tolerance. We present experimental results for the application of quantum error correction (QEC) techniques to a prototype analog computational device called a quantum emulation device. It is shown that for the gates tested (transversal Z, X and SH) there is a marked improvement in the performance characteristics of the gate operations following error correction using the 5-Qubit Perfect code. In the case of the Z gate, the median fidelity improved from 0.995 to 0.999 98, a reduction in the gate error by over two orders of magnitude. Other transverse gates similarly show strong improvements.
Highlights
Quantum information processing techniques provide an optimistic path towards the development of computational devices that can address problems for which no known efficient classical approaches are known to exist
It was found that the median fidelity for the Z gate increased to 0.999 976 4 (0.999 976 1, 0.999 976 8)
Looking at the log-fidelities given in figure 4 shows, that despite the fact that quantum errorcorrection (QEC) has a tendency to broaden the tails by periodically causing low fidelity outcomes, most of the time the procedure substantially improves the performance
Summary
Before the discovery of techniques for performing quantum errorcorrection (QEC), it was thought that the inherent fragility of quantum coherent systems would make scaling up to these sizes virtually impossible in practice. This was not unlike the situation in the early days of digital computing, when real-time error correction techniques were first contemplated [1]. For superconducting transmon qubits experimental tests have verified first-order insensitivity to induced phase-flip and bit-flip errors using three-qubit repetition codes; those same experiments found that for low error probability the overhead of QEC reduced overall performance [8]. Recent experiments on transmon qubits have demonstrated a reduction in the failure rate of input state retrieval by as much as a factor of 8.5 using multiple rounds of QEC as compared to rates for unencoded qubits [10]
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