Publications associated with Ultrafast quantum optics and optical metrology

Linear optical quantum computing in a single spatial mode.

Phys Rev Lett 111 (2013) 150501-

PC Humphreys, BJ Metcalf, JB Spring, M Moore, X-M Jin, M Barbieri, WS Kolthammer, IA Walmsley

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 [Nature (London) 409, 46 (2001)] scheme. Our protocol is suited to currently 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.

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