scholarly journals Characterization and control of open quantum systems beyond quantum noise spectroscopy

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Akram Youssry ◽  
Gerardo A. Paz-Silva ◽  
Christopher Ferrie
Keyword(s):  
Quantum Control ◽  
Performance Metrics ◽  
Quantum Noise ◽  
Open Quantum Systems ◽  
Power Spectra ◽  
General Purpose ◽  
Noise Power ◽  
Noise Spectroscopy ◽  
Quantum Technology ◽  
And Control

AbstractThe ability to use quantum technology to achieve useful tasks, be they scientific or industry related, boils down to precise quantum control. In general it is difficult to assess a proposed solution due to the difficulties in characterizing the quantum system or device. These arise because of the impossibility to characterize certain components in situ, and are exacerbated by noise induced by the environment and active controls. Here, we present a general purpose characterization and control solution making use of a deep learning framework composed of quantum features. We provide the framework, sample datasets, trained models, and their performance metrics. In addition, we demonstrate how the trained model can be used to extract conventional indicators, such as noise power spectra.

scholarly journals Demonstration of non-Markovian process characterisation and control on a quantum processor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
G. A. L. White ◽  
C. D. Hill ◽  
F. A. Pollock ◽  
L. C. L. Hollenberg ◽  
K. Modi
Keyword(s):  
Quantum Control ◽  
Scale Up ◽  
Coherence Time ◽  
Error Type ◽  
Markovian Dynamics ◽  
Quantum Device ◽  
Significant Step ◽  
Quantum Technology ◽  
And Control ◽  
Device Operation

AbstractIn the scale-up of quantum computers, the framework underpinning fault-tolerance generally relies on the strong assumption that environmental noise affecting qubit logic is uncorrelated (Markovian). However, as physical devices progress well into the complex multi-qubit regime, attention is turning to understanding the appearance and mitigation of correlated — or non-Markovian — noise, which poses a serious challenge to the progression of quantum technology. This error type has previously remained elusive to characterisation techniques. Here, we develop a framework for characterising non-Markovian dynamics in quantum systems and experimentally test it on multi-qubit superconducting quantum devices. Where noisy processes cannot be accounted for using standard Markovian techniques, our reconstruction predicts the behaviour of the devices with an infidelity of 10−3. Our results show this characterisation technique leads to superior quantum control and extension of coherence time by effective decoupling from the non-Markovian environment. This framework, validated by our results, is applicable to any controlled quantum device and offers a significant step towards optimal device operation and noise reduction.

scholarly journals Memory Effects in Quantum Dynamics Modelled by Quantum Renewal Processes

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 905
Author(s):  
Nina Megier ◽  
Manuel Ponzi ◽  
Andrea Smirne ◽  
Bassano Vacchini
Keyword(s):  
Quantum Dynamics ◽  
Open Quantum System ◽  
Open Quantum Systems ◽  
Phenomenological Approach ◽  
Quantum Systems ◽  
Renewal Processes ◽  
Continuous Part ◽  
Trace Distance ◽  
Open Quantum ◽  
And Control

Simple, controllable models play an important role in learning how to manipulate and control quantum resources. We focus here on quantum non-Markovianity and model the evolution of open quantum systems by quantum renewal processes. This class of quantum dynamics provides us with a phenomenological approach to characterise dynamics with a variety of non-Markovian behaviours, here described in terms of the trace distance between two reduced states. By adopting a trajectory picture for the open quantum system evolution, we analyse how non-Markovianity is influenced by the constituents defining the quantum renewal process, namely the time-continuous part of the dynamics, the type of jumps and the waiting time distributions. We focus not only on the mere value of the non-Markovianity measure, but also on how different features of the trace distance evolution are altered, including times and number of revivals.

scholarly journals Characterisation and Control of a Woven Biomimetic Actuator for Wearable Neurorehabilitative Devices

Actuators ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 37
Author(s):  
Vaughan Murphy ◽  
Brandon P. R. Edmonds ◽  
Ana Luisa Trejos
Keyword(s):  
Performance Metrics ◽  
Woven Fabric ◽  
Total Force ◽  
Control Methods ◽  
Soft Actuator ◽  
Sewing Thread ◽  
And Control ◽  
Fabric Mesh ◽  
Biomimetic Actuator ◽  
Multiple Units

Twisted coiled actuators (TCAs) are a type of soft actuator made from polymer fibres such as nylon sewing thread. As they provide motion in a compact, lightweight, and flexible package, they provide a solution to the actuation of wearable mechatronic devices for motion assistance. Their limitation is that they provide low total force, requiring them to actuate in parallel with multiple units. Previous literature has shown that the force and stroke production can be improved by incorporating them into fabric meshes. A fabric mesh could also improve the contraction efficiency, strain rate, and user comfort. Therefore, this study focused on measuring these performance metrics for a set of TCAs embedded into a woven fabric mesh. The experimental results show that the stroke of the actuators scaled linearly with the number of activated TCAs, achieving a maximum applied force of 11.28 N, a maximum stroke of 12.23%, and an efficiency of 1.8%. Additionally, two control methods were developed and evaluated, resulting in low overshoot and steady-state error. These results indicate that the designed actuators are viable for use in wearable mechatronic devices, since they can scale to meet different requirements, while being able to be accurately controlled with minimal additional components.

Experimental and Theoretical Comparison of the Precision of Flame Atomic Absorption, Fluorescence, and Emission Measurements

1981 ◽  
Vol 35 (3) ◽  
pp. 317-324 ◽  
Author(s):  
N. W. Bower ◽  
J. D. Ingle
Keyword(s):  
Atomic Absorption ◽  
Flicker Noise ◽  
Power Spectra ◽  
Inner Filter Effect ◽  
Atomic Emission ◽  
Noise Power ◽  
Experimental Conditions ◽  
Noise Characteristics ◽  
Fluorescence Measurements ◽  
Flame Atomic Absorption

Theoretical equations and experimental evaluation procedures for the determination of the precision of flame atomic absorption, emission, and fluorescence measurements are presented. These procedures and noise power spectra are used to evaluate the precision and noise characteristics of atomic copper measurements with all three techniques under the same experimental conditions in an H2-air flame. At the detection limit, emission and fluorescence measurements are limited by background emission shot and flicker noise whereas absorption measurements are limited by flame transmission lamp flicker noise. Analyte flicker noise limits precision at higher analyte concentrations for all three techniques. Fluctutations in self-absorption and the inner filter effect are shown to contribute to the noise in atomic emission and fluorescence measurements.

Thermodynamics and Control of Open Quantum Systems

2021 ◽  
Author(s):  
Gershon Kurizki ◽  
Abraham G. Kofman
Keyword(s):  
Quantum Chemistry ◽  
Quantum Physics ◽  
Open Quantum Systems ◽  
Condensed Matter ◽  
Quantum Systems ◽  
Open Quantum ◽  
Heat Engines ◽  
Chemistry Research ◽  
And Control ◽  
Quantum Thermodynamic

The control of open quantum systems and their associated quantum thermodynamic properties is a topic of growing importance in modern quantum physics and quantum chemistry research. This unique and self-contained book presents a unifying perspective of such open quantum systems, first describing the fundamental theory behind these formidably complex systems, before introducing the models and techniques that are employed to control their quantum thermodynamics processes. A detailed discussion of real quantum devices is also covered, including quantum heat engines and quantum refrigerators. The theory of open quantum systems is developed pedagogically, from first principles, and the book is accessible to graduate students and researchers working in atomic physics, quantum information, condensed matter physics, and quantum chemistry.

102 Single-Prolonged Stress as a Model of PTSD in Mice: Effects on Sleep and Anxiety

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A42-A42
Author(s):  
Katelyn Gutowsky ◽  
Carolyn Jones ◽  
Miranda Lim
Keyword(s):  
Rem Sleep ◽  
Sleep Disturbances ◽  
Sleep Problems ◽  
Power Spectra ◽  
Post Traumatic Stress ◽  
Sleep State ◽  
Single Prolonged Stress ◽  
Post Traumatic ◽  
And Control ◽  
Prolonged Stress

Abstract Introduction Sleep problems are common in humans with post-traumatic stress disorder (PTSD). Rapid eye movement (REM) sleep is involved in processing emotional memories; it is often disrupted in those with PTSD, and may be related to increased anxiety. Single prolonged stress (SPS) is a protocol used to model PTSD in rats, however little is known about how this model impacts sleep in mice. Prior research suggests SPS produces short term disturbances in REM sleep and increases in anxiety-like behavior, but further validation of this model is needed to understand how SPS impacts sleep and anxiety-like behaviors in mice specifically, as they have greater potential for transgenic manipulation Methods C57BL6/J mice underwent a SPS protocol in which they were tube-restrained for 2 hours, followed by a 15 minute forced swim in a group, ether exposure until loss of consciousness, and 10 days of social isolation. Following SPS, mice were tested for anxiety-like behavior in a light-dark box and sleep was measured from surgically implanted EEG and EMG leads. Time spent in wake, REM sleep, and non-REM sleep was quantified for 24 continuous hours in SPS and Control mice. Results There were no significant effects of SPS on the amount of time spent in any vigilance state, or in sleep-wake transitions. However, SPS-exposed mice showed significantly more anxiety-like behavior. EEG power spectra were analyzed in relevant frequency bands during each sleep state, and exploratory analyses were conducted Conclusion Minimal effects on sleep macroarchitecture were seen in mice 10 days after SPS. It is possible that sleep disturbances seen immediately after trauma exposure (such as in prior studies in rats) may have diminished over time. Further studies will need to include additional timepoints and analysis of sleep microarchitecture following SPS, and in other mouse models of PTSD, in order to more comprehensively examine changes in sleep. Support (if any) VA CDA #IK2 BX002712, Portland VA Research Foundation, Medical Research Foundation

scholarly journals Noise masking method based on an effective ratio mask estimation in Gammatone channels

2018 ◽  
Vol 7 ◽  
Author(s):  
Feng Bao ◽  
Waleed H. Abdulla
Keyword(s):  
Signal To Noise Ratio ◽  
Estimation Method ◽  
Wiener Filter ◽  
Power Spectra ◽  
Auditory Scene Analysis ◽  
Accurate Estimation ◽  
Noise Power ◽  
Noise Masking ◽  
Time Frequency ◽  
Mask Estimation

In computational auditory scene analysis, the accurate estimation of binary mask or ratio mask plays a key role in noise masking. An inaccurate estimation often leads to some artifacts and temporal discontinuity in the synthesized speech. To overcome this problem, we propose a new ratio mask estimation method in terms of Wiener filtering in each Gammatone channel. In the reconstruction of Wiener filter, we utilize the relationship of the speech and noise power spectra in each Gammatone channel to build the objective function for the convex optimization of speech power. To improve the accuracy of estimation, the estimated ratio mask is further modified based on its adjacent time–frequency units, and then smoothed by interpolating with the estimated binary masks. The objective tests including the signal-to-noise ratio improvement, spectral distortion and intelligibility, and subjective listening test demonstrate the superiority of the proposed method compared with the reference methods.

Thermopower and 1/f Noise Measurements in Amorphous Silicon-Carbon Alloys

1995 ◽  
Vol 377 ◽  
Author(s):  
H. M. Dyalsingh ◽  
G. M. Khera ◽  
J. Kakalios
Keyword(s):  
Amorphous Silicon ◽  
Power Spectra ◽  
Carbon Films ◽  
Noise Power ◽  
Mobility Edge ◽  
Silicon Carbon ◽  
Noise Measurements ◽  
Noise Statistics ◽  
Hydrogenated Amorphous ◽  
Q Function

ABSTRACTThermopower, conductivity and 1/f noise measurements have been performed on a series of n-type doped hydrogenated amorphous silicon carbon films that are prepared with varying gas phase concentrations of CH4. The increased disorder at the mobility edge associated with alloying is characterized by the Q-function, which is obtained by combining thermopower and conductivity measurements, and is also reflected in the noise power spectra and noise statistics.

scholarly journals Local Spin and Open Quantum Systems: Clarifying Misconceptions, Unifying Approaches

2020 ◽  
Author(s):  
Angel Martín Pendás ◽  
Evelio Francisco
Keyword(s):  
Quantum Control ◽  
Open Systems ◽  
Open Quantum Systems ◽  
Real Space ◽  
Quantum Systems ◽  
Spin Coupling ◽  
Molecular Systems ◽  
Open Quantum ◽  
Local Spin

<p>We now show that Clark and Davidson local spins operators are perfectly defined subsystem operators if a fragment is taken as an <i>open quantum system</i> (OQS). Open systems have become essential in quantum control and quantum computation, but have not received much attention in Chemistry. We have already shown (<i>J. Chem. Theory Comput</i>. <b>2018</b>, <i>15</i>, 1079) how real space OQSs can be defined in molecular systems and how they offer new insights relating quantum mechanical entaglement and chemical bonding. The OQS account of local spin that we offer yields a rigorous, yet easily accessible way to rationalize local spin values. A fragment is found in a mixed state direct sum of sectors characterized by different number of electrons that occur with different probabilities. The local spin is then a weighted sum of otherwise standard <i>S</i>(<i>S</i>+1) values. With OQS glasses, it is obvious that atomic or fragment spins should not vanish. Our approach thus casts doubts on any procedure used to annihilate them, like those used by Mayer and coworkers. OQS local spins allow for a fruitful use of models. One can propose easily sector probabilities for localized, covalent, ionic, zwitterionic, etc. situations, and examine their ideal local spins. We have mapped all 2c-2e cases, and shown how to do that in general multielectron cases. The role of electron correlation is also studied by tuning the Hubbard U/t parameter for H chains. Correlation induced localization changes the spin-coupling patterns even qualitatively, and show how the limiting antiferromagnet arises.</p>

Sign in / Sign up

Export Citation Format

Share Document