arXiv subjects

Piotr Marciniec

Publications and source records attributed to Piotr Marciniec.

4 recordsLinked to original sources

arXiv2026

Direct measurement of the energy spectrum of a quantum dot qubit

The mapping between gate voltages applied to a double quantum dot, and the parameters of a Hubbard-like Hamiltonian, is of utmost importance for understanding and operating spin qubits. State-of-the-art techniques for measuring Hamiltonian parameters (e.g., detuning axis pulsed spectroscopy, DAPS) provide details about energy levels; however, tunnel coupling estimates typically reveal only a small portion of the full Hamiltonian. Here, we demonstrate a Hamiltonian-agnostic technique for measuring the double dot energy spectrum over a wide energy range, at every value of the detuning, called delta-axis spectroscopy (DAXS). We apply the DAXS method to obtain the energy spectrum of a Si/SiGe double quantum dot and use this data to extract the diagonal and off-diagonal couplings of a 15-level Hubbard-like Hamiltonian, demonstrating very good agreement with the experimental measurements.

quant-ph↗

arXiv2025

Fast high-fidelity baseband reset of a latched state for quantum dot qubit readout

A common method for reading out the state of a spin qubit is by latching one logical qubit state, either $|1\rangle$ or $|0\rangle$, onto a different, metastable charge state. Such a latched state can provide a superior charge sensing signal for qubit readout, and it can have a lifetime chosen to be long enough that the charge sensed readout can be high fidelity. However, the passive reset out of latched states is inherently long, which is not desirable. In this work, we demonstrate an on-demand, high fidelity (> 99%) re-initialization of a quantum dot qubit out of a latched readout state. The method is simple to apply as it involves a single baseband voltage pulse to a specific region in the quantum dot stability diagram where the relaxation time from the latched state to the ground state is over 50 times faster. We describe the mechanism for the reset process as well as the boundaries for the optimal reset region in the qubit gate voltage space.

cond-mat.mes-hall↗

arXiv2025

Ultra-dispersive resonator readout of a quantum-dot qubit using longitudinal coupling

We perform readout of a quantum-dot hybrid qubit coupled to a superconducting resonator through a parametric, longitudinal interaction mechanism. Our experiments are performed with the qubit and resonator frequencies detuned by $\sim$10 GHz, demonstrating that longitudinal coupling can facilitate semiconductor qubit operation in the 'ultra-dispersive' regime of circuit quantum electrodynamics.

cond-mat.mes-hall↗

arXiv2023

Longitudinal coupling between a Si/SiGe quantum dot and an off-chip TiN resonator

Superconducting cavities have emerged as a key tool for measuring the spin states of quantum dots. So far however, few experiments have explored longitudinal couplings between dots and cavities, and no solid-state qubit experiments have explicitly probed the "adiabatic" regime, where the Purcell decay is strongly suppressed. Here, we report measurements of a double-quantum-dot charge qubit coupled to a high-impedance resonator via a "flip-chip" design geometry. By applying an adiabatic ac drive to the qubit through two different channels, and studying the effects of qubit energy detuning, interdot tunneling, and driving strength, we are able to unequivocally confirm the presence of a longitudinal coupling between the qubit and cavity, while the qubit remains in its ground state. Since this coupling is proportional to the driving amplitude, and is therefore switchable, it has the potential to become a powerful new tool in qubit experiments.

quant-ph↗