High-dimensional optical quantum logic in large operational spaces

• Main Authors: Imany, Poolad, Jaramillo-Villegas, Jose A, Alshaykh, Mohammed S, Lukens, Joseph M, Odele, Ogaga D, Moore, Alexandria J, Leaird, Daniel E, Qi, Minghao, Weiner, Andrew M
• Format: Journal Article
• Language: English
• Published: 02-08-2019
• Subjects: Physics - Quantum Physics
• DOI: 10.48550/arxiv.1805.04410

npj Quantum Information 5, 59 (2019) The probabilistic nature of single-photon sources and photon-photon
interactions encourages encoding as much quantum information as possible in
every photon for the purpose of photonic quantum information processing. Here,
by encoding high-dimensional units of information (qudits) in time and
frequency degrees of freedom using on-chip sources, we report deterministic
two-qudit gates in a single photon with fidelities exceeding 0.90 in the
computational basis. Constructing a two-qudit modulo SUM gate, we generate and
measure a single-photon state with non-separability between time and frequency
qudits. We then employ this SUM operation on two frequency-bin entangled
photons, each carrying two 32-dimensional qudits, to realize a four-party
high-dimensional Greenberger-Horne-Zeilinger state, occupying a Hilbert space
equivalent to that of 20 qubits. Although high-dimensional coding alone is
ultimately not scalable for universal quantum computing, our design shows the
potential of deterministic optical quantum operations in large encoding spaces
for practical and compact quantum information processing protocols.