Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V35: Semiconductor Qubits: Spin Qubit Read-outInvited Live
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Sponsoring Units: DQI Chair: John Nichol, University of Rochester |
Thursday, March 18, 2021 3:00PM - 3:36PM Live |
V35.00001: Charge noise and overdrive effects in dispersive readout of charge and spin qubits Invited Speaker: Andras Palyi Solid-state qubits incorporating quantum dots can be read out by gate reflectometry. In this theory talk, I will describe physical mechanisms that render such reflectometry-based readout schemes imperfect, focusing on semiconductor charge qubits and singlet-triplet spin qubits. In our model, we account for readout errors due to slow charge noise, and due to overdriving, when a too strong probe is causing errors. A key result is that the readout fidelity saturates at large probe strengths. We also point out the existence of severe readout errors appearing in a resonance-like fashion as the pulse strength is increased, and show that these errors are related to probe-induced multi-photon transitions. Besides providing practical guidelines toward optimized readout, the results I present might also inspire ways to use gate reflectometry for device characterization. |
Thursday, March 18, 2021 3:36PM - 4:12PM Live |
V35.00002: Scaling up semiconductor spin qubits Invited Speaker: Lieven Vandersypen In this talk, I will present our vision of a large-scale spin-based quantum processor, and ongoing work to realize this vision. First, we create local registers of increasing numbers of spin qubits in quantum dot arrays with sufficient control that we can program arbitrary sequences of operations. Furthermore, in close collaboration with Intel, we have measured quantum dot qubits fabricated using all-optical lithography and industrial process technology on a 300 mm wafer. This industrial approach to nanofabrication will be critical for achieving the extremely high yield necessary for devices containing hundreds or thousands of qubits. Second, we explore the coherent coupling of spin qubits at a distance via two routes. In the first approach, the electron spins remain in place and are coupled via a superconducting resonator. In the second approach, spins are shuttled along a quantum dot array, preserving both the spin projection and spin phase. Third, we work towards the integration of quantum bits and classical electronics on the same chip or package, where qubits are operated above 1 K and the electronics is designed for cryogenic operation. When combined, the progress along these various fronts can lead the way to scalable networks of high-fidelity spin qubit registers for computation and simulation. |
Thursday, March 18, 2021 4:12PM - 4:48PM Live |
V35.00003: High-performance exchange-only qubits in the SLEDGE architecture Invited Speaker: Jacob Blumoff Existing architectures for silicon quantum-dot qubits have enabled high-fidelity state preparation and measurement1, low-error randomized benchmarking2, and millisecond-scale dynamical decoupling3. To facilitate improved control of the underlying electrostatic potential and scaling to larger arrays, we present a more advanced design called Single-Layer Etch-Defined Gate Electrode, or “SLEDGE.” These devices feature a single layer of non-overlapping gate electrodes and employ vias to break the plane to backend routing. Using this process, we demonstrate exchange-only qubit initialization, measurement, and randomized benchmarking with fidelities that compare favorably to the previous design. This architecture provides a path to scalable and high-performance silicon-based quantum devices. |
Thursday, March 18, 2021 4:48PM - 5:24PM Live |
V35.00004: Quantum non-demolition spin measurement in quantum dots Invited Speaker: Jun Yoneda Single-shot measurement of spin qubits in quantum dots is now common practice. However, a quantum non-demolition (QND) implementation will be necessary in a large-scale quantum computing device e.g. for quantum error correction. In the QND spin readout, only minimal disturbance is imposed to the probed spin polarization. Therefore, unlike conventional destructive counterparts, measurements can be repeated to extinguish errors and the readout process serves as a qubit preparation device. Unfortunately, it is challenging to maintain the qubit coherence and integrity when the system is inevitably exposed to the external circuitry for readout. This stringent condition for QND measurement has been achieved in several recent experiments [1-3] for the first time in quantum dots for a different type of spin measured in each case: a single electron spin in GaAs [1] and Si [3] and a single Si-29 nuclear spin [2]. We will discuss how the high non-demolition fidelity is realized to allow for readout repetitions of a single spin state and how consecutive QND readout outcomes can be collectively used to maximize the measurement and preparation fidelities, with the main focus on the Si electron spin qubit case [3]. These results will be important for measurement-based quantum information protocols in quantum dots. |
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