[Paper Review] QUICK$^3$ -- Design of a satellite-based quantum light source for quantum communication and extended physical theory tests in space

Najme Ahmadi, S. Schwertfeger+20 more|arXiv (Cornell University)|Jan 26, 2023

Quantum Information and Cryptography67 references4 citations

TL;DR

QUICK$^3$ presents the design of a compact, satellite-based true single photon source using hexagonal boron nitride (hBN) color centers, optically excited by a diode laser and coupled to an integrated photonic circuit for on-chip photon routing. The mission, scheduled for 2024 launch on a 3U CubeSat, enables high-rate quantum key distribution and tests Born’s rule in space, demonstrating the feasibility of on-orbit quantum light sources for future quantum networks.

ABSTRACT

Modern quantum technologies have matured such that they can now be used in space applications, e.g., long-distance quantum communication. Here, we present the design of a compact true single photon source that can enhance the secure data rates in satellite-based quantum key distribution scenarios compared to conventional laser-based light sources. Our quantum light source is a fluorescent color center in hexagonal boron nitride. The emitter is off-resonantly excited by a diode laser and directly coupled to an integrated photonic processor that routes the photons to different experiments performed directly on-chip: (i) the characterization of the single photon source and (ii) testing a fundamental postulate of quantum mechanics, namely the relation of the probability density and the wave function (known as Born's rule). The described payload is currently being integrated into a 3U CubeSat and scheduled for launch in 2024 into low Earth orbit. We can therefore evaluate the feasibility of true single photon sources and reconfigurable photonic circuits in space. This provides a promising route toward a high-speed quantum network.

Motivation & Objective

• To develop a compact, reliable true single photon source suitable for deployment in low Earth orbit.
• To enable high-speed satellite-based quantum key distribution (QKD) by replacing conventional weak coherent laser pulses with true single photons.
• To test the validity of Born’s rule—the postulate linking wave function amplitude to measurement probability—under microgravity and space conditions.
• To demonstrate the integration of on-chip photonic circuits with quantum emitters and space-qualified electronics in a 3U CubeSat platform.
• To establish a scalable, modular payload architecture for future quantum space missions and commercial quantum networks.

Proposed method

• A fluorescent color center in hexagonal boron nitride (hBN) serves as the single photon emitter, excited off-resonantly by a diode laser to minimize decoherence.
• The emitted photons are directly coupled into a photonic integrated circuit (PIC) that routes light to two on-chip experiments: source characterization and Born’s rule testing.
• The system includes a laser suppression filter to minimize background noise and a tunable microcavity to enhance emission directionality and brightness.
• A reconfigurable photonic processor enables dynamic routing of photons to different measurement paths for both calibration and foundational physics experiments.
• The payload is designed for integration into a 3U CubeSat, with radiation-hardened electronics, thermal control, and a stable optical alignment system for in-orbit operation.
• Density functional theory (DFT) simulations were used to identify hBN defect configurations compatible with alkali vapor transitions, enabling future coupling to quantum memories without frequency conversion.

Experimental results

Research questions

• RQ1 Can a true single photon source based on hBN color centers operate reliably in the space environment, including microgravity and radiation exposure?
• RQ2 Does the on-chip photonic integrated circuit maintain high-fidelity photon routing and low loss under orbital conditions?
• RQ3 Can Born’s rule be tested with high precision using single photons generated in space, and does it hold under reduced gravity and long-term exposure?
• RQ4 To what extent can the integration of a compact, on-chip quantum photonic system with a satellite bus enable scalable quantum communication infrastructure?
• RQ5 Can the system achieve sufficient photon collection efficiency and brightness to support high-data-rate QKD in low Earth orbit?

Key findings

• The payload has been designed and is currently being manufactured for integration into a 3U CubeSat, with launch scheduled for 2024.
• The hBN-based single photon source is expected to significantly enhance secure data rates in satellite QKD by eliminating multi-photon pulses and enabling true single-photon operation.
• The photonic integrated circuit enables on-chip routing of photons to two distinct experiments: source characterization and Born’s rule testing, with no need for external optical switching.
• The system is designed to operate in low Earth orbit with a stable, radiation-tolerant configuration, including a laser suppression filter and thermal management.
• DFT simulations have identified specific hBN defect configurations (e.g., Er${}_{ ext{B}}$V${}_{ ext{B}}$, Ti${}_{ ext{N}}$V${}_{ ext{B}}$) that are compatible with alkali vapor transitions, enabling future direct coupling to quantum memories without frequency conversion.
• The mission represents the first planned demonstration of a true single photon source in space, paving the way for future quantum networks and fundamental physics experiments in orbit.