Bridging the Gap Between Semiconductor Photons and Atomic Memory

In an important advance, researchers have successfully interfaced two promising platforms for quantum technologies — semiconductor quantum dots and atomic quantum memories. Led by Dr. Sarah Thomas of Imperial College London, the international collaboration demonstrated the capacity to efficiently store light emitted by an indium arsenide quantum dot and retrieve it on demand using an atomic memory based on rubidium vapor.

Quantum dots are nanoscale semiconductor crystals with exceptional abilities as deterministic single photon emitters and sources of quantum entanglement. However, integrating them into large-scale quantum networks requires an interface to atomic systems capable of maintaining and manipulating photonic quantum states. Atomic memories in warm vapors offer high storage efficiencies and bandwidth well-matched to quantum dots, but challenges lie in harmonizing the spectral and temporal profiles of both.

To overcome this, the team designed their quantum dots to emit near 1529 nanometers, aligned with their rubidium memory. Photons were filtered temporally via an electro-optic modulator and spectrally using a Fabry-Pérot cavity to optimize resemblance between input and memory modes. Impressively, they achieved near 13% total efficiency and an 18+ signal-to-noise ratio limited solely by detector noise.

Further enhancements could boost performance, such as minimizing charge-induced broadening of quantum dot emission lines. The scientists proposed approaches like optical pumping, dynamic Stark shifts, or mapping to hyperfine levels eliminating Doppler dephasing to enable storage surpassing excited state lifetimes up to one second.

This landmark achievement bridges the gap between semiconductor photons and atomic memories. The ability to faithfully link distinct quantum systems represents a major milestone bringing together two leading platforms. Continued refinement of these interfaces promises to accelerate progress in developing practical quantum technologies like distributed memory nodes connecting to telecom fiber networks via quantum dots – this would in theory be the quantum internet. 

Reference(s)

1. Sarah E. Thomas, Lukas Wagner, Raphael Joos, Robert Sittig, Cornelius Nawrath, Paul Burdekin, Ilse Maillette de Buy Wenniger, Mikhael J. Rasiah, Tobias Huber-Loyola, Steven Sagona-Stophel, Sven Höfling, Michael Jetter, Peter Michler, Ian A. Walmsley, Simone L. Portalupi, Patrick M. Ledingham. Deterministic storage and retrieval of telecom light from a quantum dot single-photon source interfaced with an atomic quantum memory. Science Advances, 2024; 10 (15) DOI: 10.1126/sciadv.adi7346

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PHYSICS | QUANTUM | QUANTUM COMPUTER | QUANTUM MEMORY | SEMICONDUCTORS