Baiwang Forum 39: A quantum dot based spin-photon interface for quantum technologies
Quantum photonic technologies require processing and transport of photonic states containing superposition and entanglement information. For many applications, the ability to transfer the full quantum state of a static particle to a photonic state is crucial. For instance, static qubits can enable indirect photon-photon interactions, and transfer of entanglement between static qubits and photons allows longer distance communications.
In this presentation I will discuss progress on using self assembled quantum dots containing electron spin qubits as a spin-photon interface. I will briefly discuss progress on ultra-bright micropillar cavities with designs demonstrating 69% efficiency and predicting >90% efficiency , and previous progress on achieving deterministic interactions between a photon and a quantum dot state . I will then discuss our latest work demonstrating a transfer of the coherent state of an electron spin precessing in a magnetic field to the state of a photon. The coherent state is imprinted onto a narrow bandwidth photon as a phase modulation that oscillates at the electron spin precision frequency. Moreover, for this transfer to occur the spin and photon become entangled with each other in a non-trivial way. To the best of our knowledge no similar phenomenon has been reported in atomic or other quantum emitter systems, but may hold the key to transfer of complex quantum state of light between light and matter systems.
 Gines et al., “High Extraction Efficiency Source of Photon Pairs Based on a Quantum Dot Embedded in a Broadband Micropillar Cavity” Phys Rev Lett 129, 033601 (2022)
 P. Androvitsaneas et al. “Efficient Quantum Photonic Phase Shift in a Low Q-Factor Regime”. ACS Photonics 6, 429–435 (2019)
Prof Ruth Oulton is a Professor of Quantum Photonics at the University of Bristol and is currently Research Director for the School of Physics at the University of Bristol. She is currently developing semiconductor quantum mechanical devices that will form the first reliable quantum sources of light such as single photons sources and single photon switches. These are key components in the up-and-coming quantum technologies, for use in secure communications and in novel quantum simulation techniques that solve classically intractable calculations. Prof. Oulton has a wide interest in light-matter interactions, and her other work includes investigations of how optical interference effects in plants improve photosynthesis, and how plastic molecules called j-aggregates can have the optical properties of metals. Prof. Oulton studied at the University of Manchester (UMIST), and undertook her PhD in Sheffield on the optics of semiconductor quantum dots. She was formerly an EPSRC Career Acceleration Fellow and a Quantum Technologies Fellow, and held an Alexander von Humboldt fellowship in TU Dortmund, Germany. In a recent European network, COST Action 1403 “Nanoscale Quantum Optics”, she was the gender balance advisor and implemented interventions to start the conversation about gender inequality in the quantum technologies sector.