Spatial Mode Encoding for Quantum Key Distribution: From Hundreds to Thousands of Modes

Abstract

Here, we present a proof-of-principle high-dimensional quantum key distribution (QKD) protocol utilizing the position and momentum entanglement of photon pairs. The protocol exploits the fact that position and momentum form mutually unbiased bases, linked via a Fourier transform. One photon of the entangled pair is measured by the sender in a randomly chosen basis-either position or momentum-selected passively via a beam splitter. This projective measurement remotely prepares the partner photon in a corresponding spatial mode, which is sent to the receiver, who similarly performs a random measurement in one of the two bases. In this implementation, we achieve a photon information efficiency of 5.07 bits per photon using 90 spatial modes, and a maximum bit rate of 0.9 Kb/s with 361 modes. To assess the scalability of this spatial-mode encoding scheme, we theoretically show that using a brighter entangled photon source along with next-generation single-photon cameras - featuring improved quantum efficiency, timing and spatial resolution - this approach could achieve 9 bits per photon at 2000 spatial modes, and a bit rate of over 700 Mb/s at 4400 modes while accounting for finite-key effects. These results quantify the opportunities and performance bounds of spatially encoded, entanglement-based QKD and provide a benchmark for future high-dimensional quantum communication systems.

9 pages, 6 figures

References in corpus (31)

• Quantum entanglement
• Experimental quantum teleportation
• Quantum cryptography: Public key distribution and coin tossing
• Satellite-to-ground quantum key distribution
• Security of quantum key distribution using d-level systems
• Advances in Photonic Quantum Sensing
• High-Dimensional Intra-City Quantum Cryptography with Structured Photons
• Quantum Cryptography using larger alphabets
• Analysis and interpretation of high transverse entanglement in optical parametric down conversion
• Provably-Secure and High-Rate Quantum Key Distribution with Time-Bin Qudits
• Security Proof for Quantum Key Distribution Using Qudit Systems
• A Hierarchy of Information Quantities for Finite Block Length Analysis of Quantum Tasks
• Security of Quantum Key Distribution with Entangled Photons Against Individual Attacks
• Overcoming Noise in Entanglement Distribution
• Distributed Quantum Sensing Using Continuous-Variable Multipartite Entanglement
• A kilopixel array of superconducting nanowire single-photon detectors
• Advances in device-independent quantum key distribution
• Microsatellite-based real-time quantum key distribution
• Introduction to the Transverse Spatial Correlations in Spontaneous Parametric Down-Conversion through the Biphoton Birth Zone
• Coincidence velocity map imaging using Tpx3Cam, a time stamping optical camera with 1.5 ns timing resolution
• Composability in quantum cryptography
• A superconducting-nanowire single-photon camera with 400,000 pixels
• Transverse Entanglement Migration in Hilbert Space
• Imaging and time stamping of photons with nanosecond resolution in Timepix based optical cameras
• Experimental investigation of high-dimensional quantum key distribution protocols with twisted photons
• High-fidelity spatial mode transmission through a 1-km-long multimode fiber via vectorial time reversal
• Improving cold-atom sensors with quantum entanglement: Prospects and challenges
• Experimental investigation of quantum key distribution with position and momentum of photon pairs
• Characterisation of a single photon event camera for quantum imaging
• Entanglement from tensor networks on a trapped-ion QCCD quantum computer
• High-dimensional quantum key distribution using a multi-plane light converter