Abstract
Quantum computation and simulation requires strong coherent coupling between qubits, which may be spatially separated. Achieving this coupling for solid-state based spin qubits is a long-standing challenge. Here we theoretically investigate a method for achieving such coupling, based on superconducting nano-structures designed to channel the magnetic flux created by the qubits. We detail semi-classical analytical calculations and simulations of the magnetic field created by a magnetic dipole, depicting the spin qubit, positioned directly below nanofabricated apertures in a superconducting layer. We show that such structures could channel the magnetic flux, enhancing the dipole-dipole interaction between spin qubits and changing its scaling with distance, thus potentially paving the way for controllably engineering an interacting spin system.
Highlights
Solid-state qubits have emerged as a potential quantum information processing architecture, with leading candidates such as atomic defects in bulk materials [1] and quantum dots [2]
We show that such structures could channel the magnetic flux, enhancing the dipole-dipole interaction between spin qubits and changing its scaling with distance, potentially paving the way for controllably engineering an interacting spin system
This work addresses the challenge of achieving strong magnetic coupling between magnetic dipoles, a major obstacle for scaling spin-based qubits, and an important aspect of nonlocal magnetic sensing
Summary
Solid-state qubits have emerged as a potential quantum information processing architecture, with leading candidates such as atomic defects in bulk materials [1] and quantum dots [2]. The direct magnetic coupling between spin qubits via the dipole-dipole interaction is relevant only for spins that are quite close (at the scale of 10 nm), as this interaction usually decays with the distance cubed This has been demonstrated, e.g., for both nitrogen-vacancy (NV) centers in diamond [5,6] and for quantum dots [7,8]. Applications in quantum computing will require a high number of coupled qubits which can be addressed This would be much easier to implement if the qubits are spatially separated to much longer distances than usually possible with dipole-dipole interaction. This structure, with a ferromagnet instead of a superconductor, has already been proposed as a possible way to create long-range coherent interaction between NV centers [13]. Numerical solutions are usually either for bulk samples [26] or simple geome-
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