Coherent coupling between a quantum dot and a donor in silicon

Abstract

Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a 31P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a logical qubit encoded in the spin singlet and triplet states of the two-electron system. We show that the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit.

Surface code architecture for donors and dots in silicon with imprecise and nonuniform qubit couplings

“…1 of the main text we have shown a diagram of a donor/dot array in which the exchange interaction is controlled by a back gate below the donors. However, a fully planar arrangement in which the donors are closer to the Si/SiO 2 interface and couple laterally to the dots, as suggested by Carroll and coworkers 44 may be preferable from a fabrication viewpoint. This approach would be closest to current practice for classical silicon circuits, and it would eliminate the need for complex device layers contacted from both sides.…”

A single-atom quantum memory in silicon

“…Recent experiments have shown the great potential of donor qubits for quantum information processing [7,14,10,15,11,16,17,18,19,20,21], and some new proposals for large-scale architectures based on 31 P suggest the swapping of quantum states between electron and nucleus to optimize gate speeds and operation fidelities [22,23]. Storage of the classical [24] or the quantum [25] state of P electron spins onto their 31 P nuclei has been demonstrated in ensemble experiments.…”

Spin-selective electron transfer in a quantum dot array

“…These are two figures of merit that are highly desirable for a scalable quantum computing architecture. Various types of qubit operations have been demonstrated [10][11][12], including two-qubit logic gates using the exchange interaction between single spins in isotopically enriched silicon [13]. On the other hand, single-electron pumps [14][15][16][17][18][19][20] and the shuttling of single electron [21,22] in quantum dots have also been demonstrated at metrological accuracy.…”

“…In this paper, we propose a scheme for spin-selective coherent electron transfer in a quantum dot array achievable using the proven experimental techniques in single-spin shuttling [21,22] in a silicon qubit architecture [11][12][13]. The gradient of oscillating magnetic fields and controlled gate voltages are utilized to separate the electron wave function into different quantum dots in a spin-selective manner.…”