Spin-photon interfaces based on isoelectronic centers in semiconductors

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Quantum networks use photons to transport quantum states and distribute entanglement between processing nodes; they enable distributed computation and secure communications. They are built from physical interfaces converting stationary and photon qubits. Providing the clearest paths to scalability, solid-state spin qubits are actively developed as spin-photon interfaces.My group has successfully pioneered the use of isoelectronic centers (ICs), an optically-addressable semiconductor defect, as spin-photon interfaces. In the last grant cycle, we have made significant contributions to their understanding and demonstrated two strategic advantages that no other system combines: the high optical homogeneity of NV centers and the large dipole moments of epitaxial quantum dots. In addition, we have revealed the existence of light-and heavy-hole trions and demonstrated new and powerful optical control schemes. These accomplishments demonstrate our capacity to independently develop new research directions in this field. In the light of the compelling opportunities offered by ICs, this grant cycle is dedicated to further advancing the research on this spin qubit system. More specifically, I propose to elucidate spin relaxation and decoherence mechanisms and exploit their distinctive characteristics to address two outstanding issues impeding the development of semiconductor-based spin-photon interfaces:Spin coherence times in direct gap semiconductors are short. To address this issue, we take advantage of 1) the dilute nuclear spin environment offered by O and Te ICs in II-VI materials and 2) the extreme localization of the bound spin over a few nuclei. These two aspects can yield a local “nuclear-spin-free” environment where no nuclear spin is located underneath the electron or hole wavefunction, thereby suppressing this dominant decoherence mechanism.Actual schemes for optical initialization, control, and single-shot read-out are mutually incompatible. This important issue facing semiconductor nanostructures is solved by exploiting both light- and heavy-hole states in a single magnetic field configuration: light-hole trions provide the lambda structure for initialization and control and heavy-hole trions provide the cycling transition for read-out.By developing an original approach and by addressing two fundamental limitations, our research program strives for the highest scientific impact in quantum information, a prominent research field that promises to revolutionize information technologies. In the short term, this program enables students to develop outstanding experimental skills in classical and quantum optics, solid-state physics and devices, and precision instrumentation. These skills are highly sought in information and communication industry, which has been the fastest growing sector of the Canadian economy over the last ten years.