Stabilization of point-defect spin qubits by quantum wells

Abstract

Defect-based quantum systems in wide bandgap semiconductors are strong candidates for scalable quantum-information technologies. However, these systems are often complicated by charge-state instabilities and interference by phonons, which can diminish spin-initialization fidelities and limit room-temperature operation. Here, we identify a pathway around these drawbacks by showing that an engineered quantum well can stabilize the charge state of a qubit. Using density-functional theory and experimental synchrotron X-ray diffraction studies, we construct a model for previously unattributed point defect centers in silicon carbide as a near-stacking fault axial divacancy and show how this model explains these defects’ robustness against photoionization and room temperature stability. These results provide a materials-based solution to the optical instability of color centers in semiconductors, paving the way for the development of robust single-photon sources and spin qubits.

Stone–Wales defects in hexagonal boron nitride as ultraviolet emitters

“…The extended Stone-Wales line defects introduces occupied and empty bands in the fundamental band gap of pristine h-BN which effectively reduces the band gap for proximate point defects. As a consequence, the ionization energies of these point defects are reduced that can affect their photo-stability as found for divacancy defects inside stacking faults in 4H SiC 35 . Moreover, some common defects in h-BN, like carbon substitutional defects 28 , have optical transition between the in-gap defect level and band edges.…”

Quantum computing: A taxonomy, systematic review and future directions

“…For the design and implementation of qubits and quantum gates, a number of candidate material systems are being investigated. Some of the front‐runner material systems include trapped ions, 10 optical lattices, 12 solid‐state spins, 11 electron spins in gated quantum dots, 248 quantum wells, 249 quantum wire, 250 nuclear magnetic resonance (NMR), 251 solid‐state NMR, 252 molecular magnet, 253 cavity quantum electrodynamics, 254 linear optics, 255 diamond, 256 Bose–Einstein condensate, 257 rare‐earth‐metal‐ion‐doped inorganic crystal, 258 and metallic‐like carbon nanospheres, 259 among others. However, superconducting circuits have transpired as the most widely used and successful material system to‐date, although trapped ion system is also demonstrating excellent qubit fidelities and gate times.…”

Graphene Quantum Dot Crystal Serving as a Multi‐Qubit Circuit Operating at High Temperatures

“…Mathematically, the multi-dot systems are conveniently described in terms of the S-matrix formalism. [44] An electronic circuit consisting of many interacting quantum dots is represented using the S-matrix "products" [44] (see Equations (16)- (18) in Section II, Supporting Information).…”

“…There are expectations that the performance of graphene-based qubits [12,13] would prevail over their conventional counterparts. [16][17][18][19][20][21][22][23][24][25][26][32][33][34][35][36][37] On the other hand, limited understanding of basic principles of the graphene quantum devices is still preventing successful engineering of practical multi-element circuits. In particular, it is not yet well understood how the relativistic features such as pseudospin conservation and Klein tunneling [7][8][9][10] can be exploited to improve the quantum coherence, inter-element coupling efficiency, and influence the quantization phenomena.…”