Quantum state encoding in spatiotemporal modes of itinerant microwave photons

Quantum communication between distant superconducting qubits via itinerant microwave photons has been studied to realize distributed quantum computing. To enhance information capacity and fault tolerance in quantum networks, it is crucial to encode larger quantities of quantum information using auxiliary degrees of freedom of these photons.

In this work, we experimentally explore the potential of utilizing spatiotemporal degrees of freedom [1]. This approach is promising as it allows for the generation of a large family of orthogonal modes temporally overlapping along a single propagation path through waveform engineering.

By employing the photon-shaping technique based on the temporal control of a microwave-driven parametric transition between a superconducting transmon qubit and a resonator coupled to it [2,3], we generate single itinerant photons in multiple orthogonal spatiotemporal modes propagating along a waveguide coupled to the resonator. We evaluate the efficiencies of the photon emission and the mode-selective absorption via the time-reversal process at the receiver. We discuss the effectiveness of utilizing spatiotemporal modes for quantum communication between remote superconducting qubits.



[1] G. F. Peñas et al., Phys. Rev. Res. 6, 033294 (2024).

[2] M. Pechal et al., Phys. Rev. X. 4, 041010 (2014).

[3] T. Miyamura et al., 2024 APS March meeting, M53.00012 (2024).