Nanotechnology Now - Press Release: Optical demonstration of quantum fault-tolerant threshold

It is of great importance to deal with experimental errors which could occur in every step of quantum circuits, especially in the implementation of quantum computation. Generally, as a straightforward thought to handle the errors, quantum error correction requires more qubits to accomplish the correction operation. However, the fault-tolerant method, in which logical qubits are encoded with several physical qubits and the error in the physical space is allowable and is not expected to be corrected, provides another way to treat the error by excluding the qubit with errors from the encoded space. To be more precise, based on the same hardware, logical qubits could be output with a better probability in the fault-tolerant encoded circuit than that in the non-encoded circuit when the error rate is below the threshold. More importantly, the fault-tolerant circuit could be verified in a small system consisting of several qubits. And the threshold, an explicit evidence to support the success of fault-tolerant method, could be determined when comparing the output probabilities of encoded circuits and non-encoded circuits.