Linear Optical Quantum Computing in a Single Spatial Mode

TL;DR

This paper introduces a novel approach for linear optical quantum computing using time-bin encoding within a single spatial mode, enabling scalable quantum information processing with existing photonic technology.

Contribution

It proposes a new scheme for universal quantum computing in a single spatial mode using time-bin encoding, including methods for single-qubit and heralded CPhase gates.

Findings

First single spatial mode implementation of a two-qubit gate

Achieved an average fidelity of 0.84+-0.07 for the two-qubit gate

Demonstrates potential for increased quantum information capacity in fixed spatial resources

Abstract

We present a scheme for linear optical quantum computing using time-bin encoded qubits in a single spatial mode. We show methods for single-qubit operations and heralded controlled phase (CPhase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn scheme. Our scheme is suited to available photonic devices and ideally allows arbitrary numbers of qubits to be encoded in the same spatial mode, demonstrating the potential for time-frequency modes to dramatically increase the quantum information capacity of fixed spatial resources. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84+-0.07.