paper / jeremyobrien / Mar 22
Photonic cluster states encoded in polarization can be expanded by deterministically entangling additional path-encoded qubits using a polarization-path controlled-phase gate. This gate is realized stably with a Sagnac interferometer on single photons, enabling precise phase control for measurement basis adjustment. The approach is experimentally validated with a 2-photon, 3-qubit cluster state demonstrating measurement-based quantum computing properties.
quantum-physicsphotonic-cluster-statesquantum-informationmeasurement-based-quantum-computingsagnac-interferometerpath-polarization-entanglementarxiv-paper
“Entangled cluster states in photon polarization can be deterministically expanded by entangling path qubits of the same photons.”
paper / jeremyobrien / Mar 20
Commercial quantum key distribution systems, the first quantum technology, use photons to encode information with detectable eavesdropping. Future quantum technologies will include secure networks, enhanced metrology, lithography, and information processors offering exponential computational advantages. Photonics is central due to photons' high-speed transmission and low-noise properties, leveraging single photons, squeezed laser states, or both alongside photonic advances.
quantum-physicsphotonic-technologiesquantum-key-distributionquantum-computingopticsquantum-informationarxiv-paper
“Commercially available quantum key distribution systems are the first quantum technology harnessing uniquely quantum mechanical effects for core operation”
paper / jeremyobrien / Mar 4
Proposes a QKD protocol using entangled qubit pairs that operates securely in environments with unknown, slowly varying reference frames, requiring only particle delivery direction while tolerating unknown computational basis phases. Achieves asymptotic secret key rate matching the six-state protocol under white noise for two-qubit sources. Extends to higher-dimensional systems like qutrits with detailed physical implementation, enabling applications in earth-to-satellite links and photonic waveguides.
quantum-key-distributionentangled-qubitsreference-frame-independentquantum-cryptographyquant-pharxiv-paperqutrit-protocol
“The protocol generates a secure key in environments with unknown and slowly varying reference frames.”