Fan-out Estimation in Spin-based Quantum Computer Scale-up

Abstract

Solid-state spin-based qubits offer good prospects for scaling based on their long coherence times and nexus to large-scale electronic scale-up technologies. However, high-threshold quantum error correction requires a two-dimensional qubit array operating in parallel, posing significant challenges in fabrication and control. While architectures incorporating distributed quantum control meet this challenge head-on, most designs rely on individual control and readout of all qubits with high gate densities. We analysed the fan-out routing overhead of a dedicated control line architecture, basing the analysis on a generalised solid-state spin qubit platform parameterised to encompass Coulomb confined (e.g. donor based spin qubits) or electrostatically confined (e.g. quantum dot based spin qubits) implementations. The spatial scalability under this model is estimated using standard electronic routing methods and present-day fabrication constraints. Based on reasonable assumptions for qubit control and readout we estimate 102–105 physical qubits, depending on the quantum interconnect implementation, can be integrated and fanned-out independently. Assuming relatively long control-free interconnects the scalability can be extended. Ultimately, the universal quantum computation may necessitate a much higher number of integrated qubits, indicating that higher dimensional electronics fabrication and/or multiplexed distributed control and readout schemes may be the preferredstrategy for large-scale implementation.

Long-range exchange interaction between spin qubits mediated by a superconducting link at finite magnetic field

“…II, and performing a local rotation in the xyplane such that the coupling between |↑, ↓ and |↓, ↑ is entirely real (that is, to ensure there is no τ y term in H E ) we obtain the explicit expressions for the exchange Hamiltonian terms [Eq. (11)]. For the case where all processes are virtual, i.e., 1 + |E tot |, 1 + |∆ Z | < ∆, they are given by…”

“…However, such interactions are short-ranged, which heavily constrains the spatial distance between QDs and impedes scalability. As a result, engineering long-range interaction between spin-qubits in QDs has been an active field of research in recent years [8][9][10][11][12][13].…”

Investigation of room temperature ferromagnetism in transition metal doped BiFeO3

“…Room temperature ferromagnetism is a physical phenomenon that comes under the branch of condensed matter physics and works mainly on the properties of electron spin, with a view to improve speed, efficiency, and functionalities of electronic devices. Researchers are exploiting the control of single localized spin at an atomic scale in a crystal such as spin qubits [1][2][3] for quantum computation. Moreover, there is continuous research going on to explore spin dynamics and its coupling to spin transport in macro-scale systems [4,5] which provided fascinating phenomena like spin torque oscillator [6,7], spin Hall effect [8,9] and spin caloritronics [10,11], etc.…”