Non-reciprocal Pauli Spin Blockade in a Silicon Double Quantum Dot

Abstract

Spin qubits in gate-defined silicon quantum dots are receiving increased attention thanks to their potential for large-scale quantum computing. Readout of such spin qubits is done most accurately and scalably via Pauli spin blockade (PSB), however various mechanisms may lift PSB and complicate readout. In this work, we present an experimental observation of a new, highly prevalent PSB-lifting mechanism in a silicon double quantum dot due to incoherent tunneling between different spin manifolds. Through dispersively-detected magnetospectroscopy of the double quantum dot in 16 charge configurations, we find the mechanism to be energy-level selective and non-reciprocal for neighbouring charge configurations. Additionally, using input-output theory we report a large coupling of different electron spin manifolds of 7.90 µeV, the largest reported to date, indicating an enhanced spin-orbit coupling which may enable all-electrical qubit control.

Silicon spin qubits from laboratory to industry

“…Recently, the sensitivity has been greatly improved by switching to parallel resonators containing superconducting inductors [95], increasing the resonant frequency [57], and using quantum-limited amplification [96], though one obstacle remains. The tunnel couplings in the few-electron regime have been too small to enable tunneling in phase due to the rf oscillations, and instead experiments have been performed at higher charge occupancy, to increase the tunnel rates and where complex higher-order spin states have been observed [157,158], and spin T 1 times are typically shorter. Spin readout at the single-electron level has, however, been demonstrated with in-situ dispersive sensing in a Si/SiGe heterostructure device [98], achieving a fidelity of 98% in 6 µs (where the inter-dot tunnel coupling was estimated at 2 GHz).…”

Variable and orbital-dependent spin-orbit field orientations in a InSb double quantum dot characterized via dispersive gate sensing

“…3(d), and eventually increase the field B at which the predicted suppression of C q occurs. Second, when B B SO , spin relaxation rates mediated by hyperfine and SOI are hindered [44,45]. As a consequence, Pauli spin blockade traps the system in one of the excited states which do not contribute to C q .…”