Microsoft Technology Licensing, LLC

Benjamin Walter Reichardt

Krysta Marie Svore

Nicolas Guillaume Delfosse

This disclosure focuses on example embodiments of a classical approach to the problem of quantum error correction in the presence of faults. Linear codes equipped with faulty parity measurements are disclosed. Example definitions of fault tolerance are introduced and embodiments of a fault tolerant scheme are disclosed that reduce the number of parity measurements required compared with Shor method. Such schemes are well suited to be implemented in the classical control device of a quantum computer in order to ensure quantum fault tolerance.

Fault tolerant quantum error correction with linear codes

A quantum computing system is adapted to prepare a cat state in a quantum circuit with fault tolerance t and circuit depth less than or equal to 4+4t by performing a series of operations that includes: performing a sequence of joint parity measurements on individual pairs of neighboring qubits in a series of qubits entangled to form an initial cat state; repeating the sequence of measurements over at least t-rounds; and disentangling a first set of alternating qubits from the initial cat state, the prepared cat state being formed by a remaining second set of alternating qubits, the second set of alternating qubits being interlaced with the first set of alternating qubits along a line of one-dimensional connectivity, the series of operations being sufficient to guarantee that a prepared cat state is has less than or equal to t number of faults.

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Benjamin Walter Reichardt