Understanding environmental noise properties helps devise strategies to minimize decoherence rates. This study investigates decoherence in an Aharonov-Bohm quantum interferometer influenced by a radio-frequency electromagnetic (RF-EM) field and surface acoustic waves (SAW). The authors examine RF-EM field-induced phase breaking without thermal heating and identify optimal SAW conditions to minimize dephasing. Decoherence arises from electric field fluctuations associated with RF-EM fields and SAWs, enhancing charge-charge interactions.
Understanding environmental noise properties helps devise strategies to minimize decoherence rates. This study investigates decoherence in an Aharonov-Bohm quantum interferometer influenced by a radio-frequency electromagnetic (RF-EM) field and surface acoustic waves (SAW). The authors examine RF-EM field-induced phase breaking without thermal heating and identify optimal SAW conditions to minimize dephasing. Decoherence arises from electric field fluctuations associated with RF-EM fields and SAWs, enhancing charge-charge interactions.
We investigate the dependence of decoherence on the mode number M in a multiple-mode Aharonov-Bohm (AB) interferometer. The design of the AB interferometer allows us to precisely determine M by the additivity rule of ballistic conductors; meanwhile, the decoherence rate is simultaneously deduced by the variance of the AB oscillation amplitude. The AB amplitude decreases and fluctuates with depopulating M. Moreover, the normalized amplitude exhibits a maximum at a specific M (∼9). Data analysis reveals that the charge-fluctuation-induced dephasing, which depends on the geometry and the charge relaxation resistance of the system, could play an essential role in the decoherence process. Our results suggest that the phase coherence, in principle, can be optimized using a deliberated design and pave one of the ways toward the engineering of quantum coherence.
Phononic resonators are becoming increasingly important in quantum information science, both for applications in quantum computing, communication, and sensing as well as in experiments investigating fundamental physics. Here, we study the decoherence of phonons confined in a surface acoustic wave (SAW) resonator strongly coupled $(g/2\ensuremath{\pi}\ensuremath{\approx}9\phantom{\rule{0.16em}{0ex}}\mathrm{MHz})$ to a superconducting transmon qubit. By comparing experimental data with numerical solutions to the Markovian master equation, we report a surface phononic energy decay rate of ${\ensuremath{\kappa}}_{1}/2\ensuremath{\pi}=480\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$ and a pure dephasing rate of ${\ensuremath{\kappa}}_{\ensuremath{\phi}}/2\ensuremath{\pi}=180\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$. These rates are in good agreement with the level of decoherence we extract from qubit-assisted spectroscopic measurements of the SAW resonator. We additionally find that the timescales over which coherent driven dynamics and decoherence occur are comparable, highlighting the need to model the composite device as an open quantum system. We discuss possible sources of decoherence in SAW-based quantum acoustic devices and the application of these devices in future quantum acoustic dissipation engineering experiments. The decoherence characterization techniques we employ are broadly applicable for investigating and benchmarking the effects of loss and dephasing on mechanical resonators in the quantum regime.
Frequency instabilities are a major source of errors in quantum devices. This Letter investigates frequency fluctuations in a surface acoustic wave (SAW) resonator, where reflection coefficients of 14 SAW modes are measured simultaneously for more than 7 h. We report two distinct noise characteristics. Multimode frequency noise caused by interactions with two-level system (TLS) defects shows significant degrees of correlation that diminish with increased detuning. This finding agrees with the current understanding of the parasitic TLS behavior as one of the dominant noise sources in quantum devices. In addition to the TLS-induced noise, we observe strong anomalous frequency fluctuations with slow, anticorrelated dynamics. These noise bursts resemble signatures of cosmic radiation observed in superconducting quantum systems. Published by the American Physical Society 2024
Matter-wave interferometers with microparticles will enable the next generation of quantum sensors to probe minute quantum phase information. Therefore, estimating the loss of coherence and the degree of entanglement degradation for such interferometers is essential. In this paper, we provide a noise analysis in frequency-space focusing on electromagnetic sources of dephasing. We assume that our matter-wave interferometer has a residual charge or dipole which can interact with a neighboring particle in the ambience. We investigate the dephasing due to the Coulomb, charge-induced dipole, charge-permanent dipole, and dipole-dipole interactions. All these interactions constitute electromagnetically driven dephasing channels that can affect single or multiple interferometers. As an example, we apply the obtained formulas to situations with two adjacent microparticles, which can provide insight for the noise analysis in the quantum gravity-induced entanglement of masses (QGEM) protocol and the c-not gate: we compute the dephasing due to a gas of environmental particles interacting via dipole-dipole and charge-charge couplings, respectively. To obtain simple analytical dephasing formulas, we employ uniform probability distributions for the impact parameter and for the angles characterizing the relative orientation with respect to the interferometer and a Gaussian distribution for the velocities of the environmental particles. In both cases, we show that the dephasing rate grows with the number density of particles present in the vacuum chamber, as expected.
We investigate the possibility of an electromechanical which-path interferometer, in which electrons traveling through an Aharonov-Bohm ring incorporating a quantum dot in one of the arms are dephased by an interaction with the fundamental flexural mode of a radio-frequency cantilever. The cantilever is positioned so that its tip lies just above the dot and a bias is applied so that an electric field exists between the dot and the tip. This electric field is modified when an additional electron hops onto the dot, coupling the flexural mode of the cantilever and the microscopic electronic degrees of freedom. We analyze the transmission properties of this system and the dependence of interference fringe visibility on the cantilever-dot coupling and on the mechanical properties of the cantilever. The fringes are progressively destroyed as the interaction with the cantilever is turned up, in part due to dephasing arising from the entanglement of the electron and cantilever states and also due to the thermal smearing that results from fluctuations in the state of the cantilever. When the dwell time of the electron on the dot is comparable to or longer than the cantilever period, we find coherent features in the transmission amplitude. These features are washed out when the cantilever is decohered by its coupling to the environment.
In an open system, the dynamical evolution of a qubit state is non-deterministic due to stochastic noise, leading to qubit state decoherence. In the case of the dispersive circuit-QED qubit readout circuit, even when the readout resonator is far off-resonance, the qubit is still damped to some degree, causing decoherence. By using a Purcell filter, qubit loss may be reduced by several orders of magnitude.In this work, we propose to use acoustic wave filters, well-established in the Telecommunications industry, as a Purcell filter. Using acoustic wave filters, like bulk acoustic wave (BAW) or surface acoustic wave (SAW), versus the current state-of-the-art Purcell filters would provide several advantages: higher isolation of the qubit to the readout frequencies as well as being quite miniaturized compared to usual filter alternatives.In this work, we characterize a 1.5GHz LiNbO SAW resonator. The characteization is done maintaining qubit environmental conditions of single photon-level powers and milikelvin temperatures. We characterize its frequency and internal quality factor dependence on temperature and drive power.