Device Architecture for Coupling Spin Qubits via an Intermediate Quantum State

Abstract

We demonstrate a scalable device architecture that facilitates indirect exchange between singlettriplet spin qubits, mediated by an intermediate quantum state. The device comprises five quantum dots, which can be independently loaded and unloaded via tunnelling to adjacent reservoirs, avoiding charge latch-up common in linear dot arrays. In a step towards realizing two-qubit entanglement based on indirect exchange, the architecture permits precise control over tunnel rates between the singlet-triplet qubits and the intermediate state. We show that by separating qubits by ∼ 1 µm, the residual capacitive coupling between them is reduced to ∼ 7 µeV.

Microwaves in Quantum Computing

“…This latter aspect leads to crowding of gate electrodes and challenges for crosstalk mitigation. Alternative coupling schemes making use of intermediate electron states [ 32 ] are presently an active area of research. A further fruitful direction is to couple remote S-T qubits via a cavity resonator, following similar approaches to superconducting qubits [ 70 ].…”

Characterizing Quantum Devices at Scale with Custom Cryo-CMOS

“…In order to determine the suitability of our multiplexer for quantum device characterization, we connect it to the gates and ohmic contacts of a quantum dot device and perform transport measurements. A typical quantum dot device will have charging energies of around 100 µeV 17 . For a well defined quantum dot to be formed, the electrical noise and heat introduced by our proximal Cryo-CMOS multiplexer must be negligible relative to the charging energy 18 , thus quantum dot measure- ments provide a means of determining the suitability of our MUX for purpose.…”

Evaluation of synthetic and experimental training data in supervised machine learning applied to charge state detection of quantum dots

“…1. The capacitance model replicates a device made of six gates coupled to two dots, similar to device architectures used to define charge and spin qubits 20,[30][31][32][33][34][35] . A set of 2000 diagrams was generated by randomly sampling capacitances from a Gaussian distribution centred around one of several capacitance combinations generating diagrams encountered in experiments.…”

“…Our experimental data originates from quantum dots formed in InSb nanowires 19 as well as GaAs two dimensional electron gases 20,29 belled by two labels indicating the tuning regime, i.e single or double, and quality, i.e.sufficient or insufficient for subsequent tuning steps. Diagrams are labelled as sufficient if they feature clear triple points suitable for qubit parameter fine tuning procedures discussed in Ref.…”