Memory and Transduction Prospects for Silicon T Center Devices
Daniel B. Higginbottom, Faezeh Kimiaee Asadi, Camille Chartrand, Jia-Wei Ji, Laurent Bergeron, Michael L. W. Thewalt, Christoph Simon, Stephanie Simmons
The T center, a silicon-native spin-photon interface with telecommunication-band optical transitions and long-lived microwave qubits, offers an appealing new platform for both optical quantum memory and microwave-to-optical telecommunication-band transduction.A wide range of quantum memory and transduction schemes could be implemented withT center ensembles with sufficient optical depth, with advantages and disadvantages that depend sensitively on the ensemble properties.In this work we characterize T center spin ensembles to inform device design.We perform the first T ensemble optical depth measurement and calculate the improvement in center density or resonant optical enhancement required for efficient optical quantum memory.We further demonstrate a coherent microwave interface by coherent population trapping and Autler-Townes splitting.We then determine the most promising microwave and optical quantum memory protocol for such ensembles.By estimating the memory efficiency both in free space and in the presence of a cavity, we show that efficient optical memory is possible with reasonable optical density forecasts.Finally, we formulate a transduction proposal and discuss the achievable efficiency and fidelity.
The T center, a silicon-native spin-photon interface with telecommunication-band optical transitions and long-lived microwave qubits, offers an appealing new platform for both optical quantum memory and microwave-to-optical telecommunication-band transduction.A wide range of quantum memory and transduction schemes could be implemented withT center ensembles with sufficient optical depth, with advantages and disadvantages that depend sensitively on the ensemble properties.In this work we characterize T center spin ensembles to inform device design.We perform the first T ensemble optical depth measurement and calculate the improvement in center density or resonant optical enhancement required for efficient optical quantum memory.We further demonstrate a coherent microwave interface by coherent population trapping and Autler-Townes splitting.We then determine the most promising microwave and optical quantum memory protocol for such ensembles.By estimating the memory efficiency both in free space and in the presence of a cavity, we show that efficient optical memory is possible with reasonable optical density forecasts.Finally, we formulate a transduction proposal and discuss the achievable efficiency and fidelity.
The T centre, a silicon-native spin-photon interface with telecommunications-band optical transitions and long-lived microwave qubits, offers an appealing new platform for both optical quantum memory and microwave to optical telecommunications band transduction. A wide range of quantum memory and transduction schemes could be implemented on such a platform, with advantages and disadvantages that depend sensitively on the ensemble properties. In this work we characterize T centre spin ensembles to inform device design. We perform the first T ensemble optical depth measurement and calculate the improvement in centre density or resonant optical enhancement required for efficient optical quantum memory. We further demonstrate a coherent microwave interface by coherent population trapping (CPT) and Autler-Townes splitting (ATS). We then determine the most promising microwave and optical quantum memory protocol for such ensembles. By estimating the memory efficiency both in free-space and in the presence of a cavity, we show that efficient optical memory is possible with forecast densities. Finally, we formulate a transduction proposal and discuss the achievable efficiency and fidelity.
Combining the long-coherence of spin qubits and the capability to transmit information and entanglement through photons, spin-photon interfaces (SPIs) are a promising platform for networked quantum computation and long-distance quantum communication. SPIs that possess local `memory' qubits in addition to the optically coupled `communication' qubit can improve remote entanglement fidelities through brokered entanglement schemes and entanglement purification. In these schemes, it is critical to protect the memory qubit from decoherence during entanglement operations on the communications qubit. Silicon, a platform with mature microelectronic and nanophotonic fabrication, is host to the T centre, an SPI with emission in the telecommunications O-band that directly integrates with silicon nanophotonics. Cavity-coupled T centres are a platform for brokered entanglement distribution in silicon photonic circuits and over long-distance optical fibre links. The T centre's electron and nuclear spin qubits are an intrinsic register of communication and memory qubits respectively, with anisotropic hyperfine coupling. In this work we determine the T centre's hydrogen hyperfine coupling tensor. We also introduce schemes to protect against dephasing or eliminate relaxation of the T centre's hydrogen memory qubit during optical excitation. These results address a key challenge for practical T centre quantum networks.
Quantum networking is a crucial technology towards constructing large-scale distributed quantum systems. The structure of photonic link and distributed network nodes allows high-speed and high-fidelity interconnect, enabling various applications such as distributed quantum computing and sensing, as well as secure quantum communications. Optically interfaced solid-sate spins are promising candidates for building a quantum network due to their active spin-photon interfaces, compatibility, and scalability for device integration. Especially for defect spins in silicon, the platform benefits from mature silicon photonic industry, and can access to the integration techniques developed over the past decades. T center in silicon particularly holds great expectations because of the telecom-O band optical interface, ground state doublet spin manifold, and long-lived nuclear spin coherence. Their telecom spin-photon interface provides a direct link between stationary quantum memory and flying qubits that are compatible with the existing telecommunication fiber network infrastructure. This work focuses on investigating cavity quantum electrodynamics (cQED) for cavity-coupled single T centers, its applications in quantum optical control of T center optical properties, and in realizing single-shot spin state readout. The cavity enhanced light-matter interaction mitigates the caveats of T center, such as long radiative lifetime, low Debye-Waller factor, and lack of polarization selection rule for the optical transitions. In this work, by integrating single T centers with a low-loss, small mode volume silicon photonic cavity, we have achieved the Purcell enhancement for boosting the T center fluorescence rate with a factor of 6.89. We build up the theoretical framework based on the Jaynes-Cummings model and Lindblad master equation to explain experimental observations and reveal cQED parameters. The further study on the electronic spin state readout is carried out as the fast, high-fidelity single-shot readout is critical for quantum information processing. Two methods are proposed based on realistic cQED parameters: resonant fluorescence readout in the low-cooperativity regime and spin-dependent cavity-reflection readout for intermediate- and high-cooperativity regimes. Both approaches demonstrate feasibility of high-fidelity (F > 0.95) readout, particularly the reflection readout allows F > 0.99 within a short readout time of 50 μs. This work demonstrates a promising telecom spin-photon interface with high-fidelity readout based on cavity-coupled single T centers in silicon, which are promising candidates for building future large-scale quantum networks.
Over the past decade, quantum computers have emerged as a promising technology to enable transformational advances in information processing and communication and solve problems that are intractable to classical computers. While there is great promise in linking quantum computers together over long distances via quantum channels, these technologies are still under development. Solid-state emitters with coherent spin-photon interfaces, long spin lifetimes, and narrow optical transitions are a leading platform for use as quantum memories in networked quantum repeaters. However, while such emitters have already enabled advanced quantum networking demonstrations in laboratory settings, applying these devices as useful memory devices at scale is a key outstanding challenge. In this thesis, we experimentally investigate solid-state quantum memories for quantum information applications. First, we develop experimental techniques to characterize solid-state emitters with high throughput, enabling both better understanding of the distribution of emitter properties and improved feedback on material preparation and device fabrication. Next, we implement quantum frequency conversion to create a coherent spin-photon interface between silicon-vacancy centers in diamond and optical photons in the low-loss telecom band. Finally, we investigate color centers in other engineering materials, including silicon and silicon carbide, to better understand the fundamental trade space of requirements for solid-state hosts. Together, these efforts represent a significant advance in creating, controlling, and deploying telecom-compatible spin interfaces, paving the way for memory-enabled quantum repeaters.
Artificial atoms in solids are leading candidates for quantum networks, scalable quantum computing, and sensing, as they combine long-lived spins with mobile and robust photonic qubits. The central requirements for the spin-photon interface at the heart of these systems are long spin coherence times and efficient spin-photon coupling at telecommunication wavelengths. Artificial atoms in silicon have a unique potential to combine the long coherence times of spins in silicon with telecommunication wavelength photons in the world's most advanced microelectronics and photonics platform. However, a current bottleneck is the naturally weak emission rate of artificial atoms. An open challenge is to enhance this interaction via coupling to an optical cavity. Here, we demonstrate cavity-enhanced single artificial atoms at telecommunication wavelengths in silicon. We optimize photonic crystal cavities via inverse design and show controllable cavity-coupling of single G-centers in the telecommunications O-band. Our results illustrate the potential to achieve a deterministic spin-photon interface in silicon at telecommunication wavelengths, paving the way for scalable quantum information processing.
The global quantum internet will require long-lived, telecommunications band photon-matter interfaces manufactured at scale. Preliminary quantum networks based upon photon-matter interfaces which meet a subset of these demands are encouraging efforts to identify new high-performance alternatives. Silicon is an ideal host for commercial-scale solid-state quantum technologies. It is already an advanced platform within the global integrated photonics and microelectronics industries, as well as host to record-setting long-lived spin qubits. Despite the overwhelming potential of the silicon quantum platform, the optical detection of individually addressable photon-spin interfaces in silicon has remained elusive. In this work we produce tens of thousands of individually addressable `T centre' photon-spin qubits in integrated silicon photonic structures, and characterize their spin-dependent telecommunications-band optical transitions. These results unlock immediate opportunities to construct silicon-integrated, telecommunications-band quantum information networks.