Robust energy selective tunneling readout of singlet triplet qubits under large magnetic field gradient

Abstract

Fast and high-fidelity quantum state detection is essential for building robust spin-based quantum information processing platforms in semiconductors. The Pauli spin blockade (PSB)-based spin-to-charge conversion and its variants are widely used for the spin state discrimination of two-electron singlet-triplet (ST${}_0$) qubits; however, the single-shot measurement fidelity is limited by either the low signal contrast, or the short lifetime of the triplet state at the PSB energy detuning, especially due to strong mixing with singlet states at large magnetic field gradients. Ultimately, the limited single-shot measurement fidelity leads to low visibility of quantum operations. Here, we demonstrate an alternative method to achieve spin-to-charge conversion of ST${}_0$ qubit states using energy selective tunneling between doubly occupied quantum dots (QDs) and electron reservoirs. We demonstrate a single-shot measurement fidelity of 90% and an S-T${}_0$ oscillation visibility of 81% at a field gradient of 100 mT (~ 500 $MHz\cdot h\cdot (g^{\ast }\cdot {\mu }_B{)}^{-1}$); this allows single-shot readout with full electron charge signal contrast and, at the same time, long and tunable measurement time with negligible effect of relaxation even at strong magnetic field gradients. Using an rf-sensor positioned opposite to the QD array, we apply this method to two ST${}_0$ qubits and show high-visibility readout of two individual single-qubit gate operations is possible with a single rf single-electron transistor sensor. We expect our measurement scheme for two-electron spin states can be applied to various hosting materials and provides a simplified and complementary route for multiple qubit state detection with high accuracy in QD-based quantum computing platforms.

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Cited by in corpus (9)

• Review of performance metrics of spin qubits in gated semiconducting nanostructures
• Single-shot readout of a driven hybrid qubit in a GaAs double quantum dot
• Generalized figure of merit for qubit readout
• Approaching ideal visibility in singlet-triplet qubit operations using energy-selective tunneling-based Hamiltonian estimation
• Wigner-molecularization-enabled dynamic nuclear field programming
• Probing two-qubit capacitive interactions beyond bilinear regime using dual Hamiltonian parameter estimations
• Protecting coherence from the environment via Stark many-body localization in a Quantum-Dot Simulator
• True decoherence-free-subspace derived from a semiconductor double quantum dot Heisenberg spin-trimer
• Four-state discrimination for a pair of spin qubits via gate reflectometry