arXiv subjects

Si-Si Gu

Publications and source records attributed to Si-Si Gu.

5 recordsLinked to original sources

arXiv2026

On-chip Parametric Amplification in a Double Quantum Dots Circuit

In microwave-based quantum circuits, including double quantum dots (DQDs), superconducting qubits and spin qubits, parametric amplifiers are indispensable in achieving high-fidelity qubit readouts. Despite its importance, the application of parametric amplifiers is hampered by several challenges, such as high insertion losses, constrained tunability, and a pronounced vulnerability to magnetic fields. Here, we demonstrate an on-site single-atom parametric amplifier (SAPA) within a reconfigurable quantum circuit, which consists of a superconducting microwave cavity and two GaAs gate-defined DQDs. Leveraging the inherent nonlinearity of the DQD, a parametric gain exceeding 11 dB is achieved. This gain contributes to enhance the qubit readout, as evidenced by exceeding two times improvement in the signal-to-noise ratio (SNR) when employing the DQD-based amplifier for reading out another DQD. Our work not only presents a versatile experimental platform with enhanced readout capabilities in quantum computing, but also introduces alternative choices of parametric amplifiers for a variety of microwave-based quantum circuits.

quant-ph↗

arXiv2022

Probing two driven double quantum dots strongly coupled to a cavity

We experimentally and theoretically study a driven hybrid circuit quantum electrodynamics (cQED) system beyond the dispersive coupling regime. Treating the cavity as part of the driven system, we develop a theory applicable to such strongly coupled and to multi-qubit systems. The fringes measured for a single driven double quantum dot (DQD)-cavity setting and the enlarged splittings of the hybrid Floquet states in the presence of a second DQD are well reproduced with our model. This opens a path to study Floquet states of multi-qubit systems with arbitrarily strong coupling and reveals a new perspective for understanding strongly driven hybrid systems.

cond-mat.mes-hall↗

arXiv2021

Floquet state depletion in ac-driven circuit QED

We perform Floquet spectroscopy in a GaAs double quantum dot system coupled to a high-impedance superconducting resonator. By applying microwave induced consecutive passages under a double resonance condition, we observe novel Landau-Zener-Stückelberg-Majorana interference patterns that stem from a cavity-assisted interference pattern modified by the depletion of the ground state. Our experimental results reveal the stationary state behavior of a strongly driven two-level system, and are consistent with the simulations based on our theoretical model. This study provides an excellent platform for investigating the dynamics of Floquet states in the presence of strong driving.

cond-mat.mes-hall↗

arXiv2021

Microwave-resonator-detected excited-state spectroscopy of a double quantum dot

As an application in circuit quantum electrodynamics (cQED) coupled systems, superconducting resonators play an important role in high-sensitivity measurements in a superconductingsemiconductor hybrid architecture. Taking advantage of a high-impedance NbTiN resonator, we perform excited-state spectroscopy on a GaAs double quantum dot (DQD) by applying voltage pulses to one gate electrode. The pulse train modulates the DQD energy detuning and gives rise to charge state transitions at zero detuning. Benefiting from the outstanding sensitivity of the resonator, we distinguish different spin-state transitions in the energy spectrum according to the Pauli exclusion principle. Furthermore, we experimentally study how the interdot tunneling rate modifies the resonator response. The experimental results are consistent with the simulated spectra based on our model.

cond-mat.mes-hall↗

arXiv2020

Correlated spectrum of distant semiconductor qubits coupled by microwave photons

We develop a new spectroscopic method to quickly and intuitively characterize the coupling of two microwave-photon-coupled semiconductor qubits via a high-impedance resonator. Highly distinctive and unique geometric patterns are revealed as we tune the qubit tunnel couplings relative to the frequency of the mediating photons. These patterns are in excellent agreement with a simulation using the Tavis-Cummings model, and allow us to readily identify different parameter regimes for both qubits in the detuning space. This method could potentially be an important component in the overall spectroscopic toolbox for quickly characterizing certain collective properties of multiple cavity QED coupled qubits.

cond-mat.mes-hall↗