Deterministic linear-optical computing with symmetry-based qubits

TL;DR

This paper demonstrates that symmetry-based qubits in linear optical systems enable deterministic, low-resource controlled-NOT gates and programmable multi-qubit operations without post-selection or ancilla, advancing optical quantum computing.

Contribution

It introduces a symmetry-based qubit approach that allows Grover four-port multiports to implement deterministic, resource-efficient optical controlled gates and programmable quantum devices.

Findings

Achieved deterministic controlled-NOT gates using symmetry-based qubits.

Enabled programmable multi-qubit gates including Fredkin and Toffoli.

Eliminated the need for post-selection or ancilla measurements in optical gates.

Abstract

A particular type of linear optical multiport, the Grover four-port, has previously been shown to couple the spatial symmetry of a photon to its direction of travel. It is shown here that use of a nonstandard choice of qubit, based on symmetry, allows Grover four ports to act as compact, low-resource deterministic linear optical controlledNOTgates, with no post-selection or ancilla measurements required. This approach allows programmable devices, made from Grover multiports in combination with other standard optical components, that can implement multiple different one-, two-, and three-qubit gates, including the Fredkin and Toffoli gates.