Automatic Post-selection by Ancillae Thermalisation

TY - JOUR

T1 - Automatic Post-selection by Ancillae Thermalisation

AU - Booth, George

PY - 2021/5/28

Y1 - 2021/5/28

N2 - Tasks such as classification of data and determining the groundstate of a Hamiltonian cannot be carried out through purely unitary quantum evolution. Instead, the inherent non-unitarity of the measurement process must be harnessed. Post-selection and its extensions provide a way to dothis. However they make inefficient use of time resources — a typical computation might require O(2m) measurements over m qubits to reach a desired accuracy and cannot be done intermittently on current (superconducting-based) NISQ devices. We propose a method inspired by thermalisationthat harnesses insensitivity to the details of the bath. We find a greater robustness to gate noise by coupling to this bath, with a similar cost in time and more qubits compared to alternate methods for inducing non-linearity such as fixed-point quantum search for oblivious amplitude amplification. Post-selection on m ancillae qubits is replaced with tracing out O (log  = log(1    p)) (where p is the probability of a successful measurement) to attain the same accuracy as the post-selection circuit. We demonstrate this scheme on the quantum perceptron, quantum gearbox and phase estimation algorithm. This method is particularly advantageous on current quantum computers involving superconducting circuits.

AB - Tasks such as classification of data and determining the groundstate of a Hamiltonian cannot be carried out through purely unitary quantum evolution. Instead, the inherent non-unitarity of the measurement process must be harnessed. Post-selection and its extensions provide a way to dothis. However they make inefficient use of time resources — a typical computation might require O(2m) measurements over m qubits to reach a desired accuracy and cannot be done intermittently on current (superconducting-based) NISQ devices. We propose a method inspired by thermalisationthat harnesses insensitivity to the details of the bath. We find a greater robustness to gate noise by coupling to this bath, with a similar cost in time and more qubits compared to alternate methods for inducing non-linearity such as fixed-point quantum search for oblivious amplitude amplification. Post-selection on m ancillae qubits is replaced with tracing out O (log  = log(1    p)) (where p is the probability of a successful measurement) to attain the same accuracy as the post-selection circuit. We demonstrate this scheme on the quantum perceptron, quantum gearbox and phase estimation algorithm. This method is particularly advantageous on current quantum computers involving superconducting circuits.

M3 - Article

SN - 2643-1564

JO - Physical Review Research

JF - Physical Review Research

ER -