Secure Quantum Key Distribution Using a Room-Temperature Quantum Emitter (2501.13902v2)

Abstract: On-demand generation of single photons from solid-state quantum emitters is essential to build practical quantum networks and QKD systems by potentially enabling higher secure key rates (SKR) and lower quantum bit error rates (QBER) in short-range distances. Room-temperature operation is particularly important as it eliminates the need for bulky cryogenic setups, reducing complexity and cost for real-world applications. In this work, we showcase the versatility of defects in hexagonal boron nitride (hBN) at room temperature by implementing the B92 protocol. Our experiments yield a sifted key rate (SiKR) of 17.5 kbps with a QBER of 6.49% at a dynamic polarization encoding rate of 40 MHz, and finite-key analysis provides a SKR of 7 kbps, one of the highest achieved for a room-temperature single photon source. We analyzed the non-decoy efficient BB84 using our hBN emitter and other promising quantum dot source for QKD, and compare their key performance with a single quantum repeater scenario. We also explore potential applications of hBN defects beyond QKD and analyze scenarios that could outperform conventional point-to-point QKD schemes. These results underscore the promise of hBN emitters for advancing quantum communication technologies.

• The paper achieves secure QKD with a novel room-temperature hBN quantum emitter using the B92 protocol, attaining a secure key rate of 7 kbps with a QBER of 6.49%.
• It employs an advanced optical setup with high numerical aperture objectives, dynamic polarization encoding via an EOM, and temporal filtering to optimize photon detection.
• The findings highlight hBN defects as scalable alternatives to cryogenic sources, paving the way for robust quantum communication networks.

Secure Quantum Key Distribution with Room-Temperature Quantum Emitter

The paper under discussion presents an advancement in quantum key distribution (QKD) utilizing room-temperature quantum emitters, specifically focusing on defects in hexagonal boron nitride (hBN). The research demonstrates the implementation of the B92 protocol for QKD using these quantum emitters, showcasing notable performance metrics including a sifted key rate (SiKR) of 17.5 kbps and a secure key rate (SKR) of 7 kbps with a quantum bit error rate (QBER) of 6.49%, achieved at a dynamic polarization encoding rate of 40 MHz. This research identifies hBN defects as significant candidates in enhancing quantum communication systems.

The experimental setup, illustrated in the publication, involves an intricate configuration for the optical excitation of hBN defects, spectral analysis, and the verification of emitted single photons. Operating at room temperature, the setup leverages a high numerical aperture objective for excitation and emission collection, coupled with a Hanbury-Brown and Twiss interferometer to confirm single-photon emission characteristics. Key focus is given to the integration of a resonant electro-optic modulator (EOM) that enables dynamic polarization encoding of single photons. Temporal filtering strategies enhance the key rates and reduce QBER by optimizing the timing of photon detection relative to the emitter’s decay time.

This research distinctly contributes to the field of QKD by demonstrating the highest recorded SKR from a room-temperature single-photon source with active polarization encoding. The use of hBN offers advantages given its room-temperature operation and the material's capability to host optically active defects emitting across a broad spectrum from visible to near-infrared frequencies. These attributes position hBN as a versatile material for integration with quantum photonic structures, facilitating its application in various quantum technology platforms.

Theoretical implications suggest that further optimization through micro-cavity enhancements and improved collection efficiencies could significantly boost the SKR, aligning with metrics commonly associated with cryogenic quantum dot (QD) sources. Such improvements mark hBN as a potential contender for future quantum communication networks, providing practical advantages over systems requiring extensive infrastructure and low-temperature environments.

Conclusively, the implications of this work are critical in quantum communication technology, as it provides a practical path forward for QKD systems using room-temperature emitters, offering a robust alternative to traditional, more complex systems. Future developments should explore further material engineering and system integration to capitalize on the scalability and ambient operating conditions of hBN defects. The advancement of such technologies could pave the way for broader implementation of quantum networks, emphasizing the importance of continued research in room-temperature quantum emitters and their practical applications in secure communications.