Measurement-Induced State transitions in Inductively-Shunted Transmons

TL;DR

This paper investigates measurement-induced state transitions in inductively-shunted transmon qubits, demonstrating how adding an inductive shunt stabilizes these transitions and improves measurement fidelity in superconducting quantum systems.

Contribution

The study introduces an inductive shunt to transmon qubits to eliminate offset charge dependence and stabilize measurement-induced state transitions, supported by experimental and theoretical analysis.

Findings

Inductive shunt stabilizes MIST in transmons.

Experimental results agree with quantum and semiclassical models.

Method extends to other inductively-shunted qubits.

Abstract

Fast and high-fidelity qubit measurement plays a key role in quantum error correction. In superconducting qubits, measurement is typically performed using a resonant microwave drive on a readout resonator dispersively coupled to the qubit. Shorter measurement times require larger numbers of photons populating the readout resonator, which ultimately leads to undesired measurementinduced state transitions (MIST) of the qubit. MIST can be particularly problematic because these transitions often leave the qubit in a high energy state, and the MIST locations in readout parameter space drift as a function of qubit offset charge. In transmon qubits, these drifts have been avoided using very large qubit-resonator detunings or dedicated offset charge biases. In this work, we take an alternative approach and add an inductive shunt to the transmon to eliminate the offset charge dependence and stabilize the MIST. We experimentally characterize MIST in several different inductively-shunted transmons, in agreement with quantum and semiclassical models for MIST. These results extend to other inductively-shunted qubits.