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The global quantum internet will require long-lived, telecommunications-band photon–matter interfaces manufactured at scale 1 . Preliminary quantum networks based on photon–matter interfaces that meet a subset of these demands are encouraging efforts to identify new high-performance alternatives 2 . 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 3 . 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 integrate individually addressable ‘T centre’ photon–spin qubits in 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. Individually addressable ‘T centre’ photon-spin qubits are integrated in silicon photonic structures and their spin-dependent telecommunications-band optical transitions characterized, creating opportunities to construct silicon-integrated, telecommunications-band quantum information networks.

Quantum computing technologies are advancing, and the class of addressable problems is expanding. Together with the emergence of new ventures and government-sponsored partnerships, these trends will help to lower the barrier for adoption of new technology and provide stability in an uncertain market. Until then, quantum computing presents an exciting testbed for different strategies in an emerging market.Quantum computing technologies are advancing, and the class of addressable problems is expanding. What market strategies are quantum computing companies and start-ups adopting?

The spin state of the nitrogen-vacancy (NV) center in diamond offers a promising platform for the development of quantum technologies and investigations into spin dynamics at the nanoscale. With a lengthy coherence time even at room temperature, NV centers enable precision metrology with atomic scale spatial resolution and present one path towards quantum information in the solid state. These applications require coherent control of the NV center spin state, and this can be achieved with resonant magnetic fields, electric fields, or, at cryogenic temperatures, optical fields. In this thesis, we demonstrate direct mechanical control of NV center spins by coherently driving magnetically-forbidden spin transitions with the resonant lattice strain generated by a mechanical resonator. We then employ mechanical driving to perform continuous dynamical decoupling and extend the inhomogeneous dephasing time of a single NV center spin. Finally, we demonstrate and quantify a spin-strain coupling within the NV center room temperature orbital excited state and propose a dissipative protocol to cool a mechanical resonator mode using this interaction. The methods of mechanical spin control developed here unlock a new degree of freedom within the NV center Hamiltonian that may enable new sensing modes and could provide a route to NV center-mechanical resonator hybrid quantum systems.

Quantum computing technologies are advancing, and the class of addressable problems is expanding. Together with the emergence of new ventures and government-sponsored partnerships, these trends will help lower the barrier for new technology adoption and provide stability in an uncertain market. Until then, quantum computing presents an exciting testbed for different strategies in an emerging market.

Diamond-based microelectromechanical systems (MEMS) enable direct coupling between the quantum states of nitrogen-vacancy (NV) centers and the phonon modes of a mechanical resonator. One example, diamond high-overtone bulk acoustic resonators (HBARs), feature an integrated piezoelectric transducer and support high-quality factor resonance modes into the GHz frequency range. The acoustic modes allow mechanical manipulation of deeply embedded NV centers with long spin and orbital coherence times. Unfortunately, the spin-phonon coupling rate is limited by the large resonator size, \\(>100~\\mu\\)m, and thus strongly-coupled NV electron-phonon interactions remain out of reach in current diamond BAR devices. Here, we report the design and fabrication of a semi-confocal HBAR (SCHBAR) device on diamond (silicon carbide) with \\(f\\cdot Q>10^{12}\\)(\\(>10^{13}\\)). The semi-confocal geometry confines the phonon mode laterally below 10~\\(\\mu\\)m. This drastic reduction in modal volume enhances defect center electron-phonon coupling. For the native NV centers inside the diamond device, we demonstrate mechanically driven spin transitions and show a high strain-driving efficiency with a Rabi frequency of \\((2\\pi)2.19(14)\\)~MHz/V\\(_{p}\\), which is comparable to a typical microwave antenna at the same microwave power.

Commercially impactful quantum algorithms such as quantum chemistry and Shor's algorithm require a number of qubits and gates far beyond the capacity of any existing quantum processor. Distributed architectures, which scale horizontally by networking modules, provide a route to commercial utility and will eventually surpass the capability of any single quantum computing module. Such processors consume remote entanglement distributed between modules to realize distributed quantum logic. Networked quantum computers will therefore require the capability to rapidly distribute high fidelity entanglement between modules. Here we present preliminary demonstrations of some key distributed quantum computing protocols on silicon T centres in isotopically-enriched silicon. We demonstrate the distribution of entanglement between modules and consume it to apply a teleported gate sequence, establishing a proof-of-concept for T centres as a distributed quantum computing and networking platform.