scholarly journals Tangible reduction in learning sample complexity with large classical samples and small quantum system

2021 ◽  
Vol 20 (8) ◽  
Author(s):  
Wooyeong Song ◽  
Marcin Wieśniak ◽  
Nana Liu ◽  
Marcin Pawłowski ◽  
Jinhyoung Lee ◽  
...  
Keyword(s):  
Quantum System ◽  
Learning Sample ◽  
Sample Complexity ◽  
Small Quantum

scholarly journals Can small quantum systems learn

2017 ◽  
Vol 17 (7&8) ◽  
pp. 568-594
Author(s):  
Nathan Wiebe ◽  
Christopher Grandade
Keyword(s):  
Quantum Mechanics ◽  
Fault Tolerance ◽  
Bayesian Inference ◽  
Quantum System ◽  
Lower Bounds ◽  
State Vector ◽  
Quantum Systems ◽  
Posterior Distributions ◽  
Quantum Devices ◽  
Small Quantum

We examine the question of whether quantum mechanics places limitations on the ability of small quantum devices to learn. We specifically examine the question in the context of Bayesian inference, wherein the prior and posterior distributions are encoded in the quantum state vector. We conclude based on lower bounds from Grover’s search that an efficient blackbox method for updating the distribution is impossible. We then address this by providing a new adaptive form of approximate quantum Bayesian inference that is polynomially faster than its classical anolog and tractable if the quantum system is augmented with classical memory or if the low–order moments of the distribution are protected through redundant preparation. This work suggests that there may be a connection between fault tolerance and the capacity of a quantum system to learn from its surroundings.

scholarly journals Thermalization of small quantum systems: From the zeroth law of thermodynamics

2021 ◽  
Author(s):  
Jiaozi Wang ◽  
Wen-Ge Wang ◽  
Jiao Wang
Keyword(s):  
Quantum System ◽  
Chaotic Systems ◽  
Environmental Temperature ◽  
Quantum Systems ◽  
Necessary Condition ◽  
Environmental System ◽  
Small System ◽  
Composite Systems ◽  
Small Quantum

Abstract Thermalization of isolated quantum systems has been studied intensively in recent years and significant progresses have been achieved. Here, we study thermalization of small quantum systems that interact with large chaotic environments under the consideration of Schrödinger evolution of composite systems, from the perspective of the zeroth law of thermodynamics. Namely, we consider a small quantum system that is brought into contact with a large environmental system; after they have relaxed, they are separated and their temperatures are studied. Our question is under what conditions the small system may have a detectable temperature that is identical with the environmental temperature. This should be a necessary condition for the small quantum system to be thermalized and to have a well-defined temperature. By using a two-level probe quantum system that plays the role of a thermometer, we find that the zeroth law is applicable to quantum chaotic systems, but not to integrable systems.

scholarly journals The 1-Megapixel pnCCD detector for the Small Quantum Systems Instrument at the European XFEL: system and operation aspects

2021 ◽  
Vol 28 (2) ◽  
pp. 576-587
Author(s):  
Markus Kuster ◽  
Karim Ahmed ◽  
Kai-Erik Ballak ◽  
Cyril Danilevski ◽  
Marko Ekmedžić ◽  
...  
Keyword(s):  
Quantum System ◽  
Quantum Efficiency ◽  
Imaging Techniques ◽  
High Sensitivity ◽  
Low Noise ◽  
Nano Particles ◽  
Single Photons ◽  
High Quantum Efficiency ◽  
High Quantum ◽  
Small Quantum

The X-ray free-electron lasers that became available during the last decade, like the European XFEL (EuXFEL), place high demands on their instrumentation. Especially at low photon energies below 1 keV, detectors with high sensitivity, and consequently low noise and high quantum efficiency, are required to enable facility users to fully exploit the scientific potential of the photon source. A 1-Megapixel pnCCD detector with a 1024 × 1024 pixel format has been installed and commissioned for imaging applications at the Nano-Sized Quantum System (NQS) station of the Small Quantum System (SQS) instrument at EuXFEL. The instrument is currently operating in the energy range between 0.5 and 3 keV and the NQS station is designed for investigations of the interaction of intense FEL pulses with clusters, nano-particles and small bio-molecules, by combining photo-ion and photo-electron spectroscopy with coherent diffraction imaging techniques. The core of the imaging detector is a pn-type charge coupled device (pnCCD) with a pixel pitch of 75 µm × 75 µm. Depending on the experimental scenario, the pnCCD enables imaging of single photons thanks to its very low electronic noise of 3 e− and high quantum efficiency. Here an overview on the EuXFEL pnCCD detector and the results from the commissioning and first user operation at the SQS experiment in June 2019 are presented. The detailed descriptions of the detector design and capabilities, its implementation at EuXFEL both mechanically and from the controls side as well as important data correction steps aim to provide useful background for users planning and analyzing experiments at EuXFEL and may serve as a benchmark for comparing and planning future endstations at other FELs.

scholarly journals The Small Quantum System (SQS) Instrument at European XFEL: Results of commissioning and first experiments

2020 ◽  
Vol 1412 ◽  
pp. 112005
Author(s):  
M Meyer ◽  
T M Baumann ◽  
A Achner ◽  
R Boll ◽  
A De Fanis ◽  
...  
Keyword(s):  
Quantum System ◽  
Small Quantum

scholarly journals A simple, approximate method for analysis of Kerr-Newman black hole dynamics and thermodynamics

2009 ◽  
pp. 39-44
Author(s):  
V. Pankovic ◽  
S. Ciganovic ◽  
R. Glavatovic
Keyword(s):  
Black Hole ◽  
Quantum System ◽  
Approximate Method ◽  
Quantum State ◽  
Black Hole Entropy ◽  
The Other ◽  
Canonical Distribution ◽  
Small Quantum ◽  
Newman Black Hole ◽  
Ground Mass

In this work we present a simple approximate method for analysis of the basic dynamical and thermodynamical characteristics of Kerr-Newman black hole. Instead of the complete dynamics of the black hole self-interaction, we consider only the stable (stationary) dynamical situations determined by condition that the black hole (outer) horizon 'circumference' holds the integer number of the reduced Compton wave lengths corresponding to mass spectrum of a small quantum system (representing the quantum of the black hole self-interaction). Then, we show that Kerr-Newman black hole entropy represents simply the ratio of the sum of static part and rotation part of the mass of black hole on one hand, and the ground mass of small quantum system on the other hand. Also we show that Kerr-Newman black hole temperature represents the negative value of the classical potential energy of gravitational interaction between a part of black hole with reduced mass and a small quantum system in the ground mass quantum state. Finally, we suggest a bosonic great canonical distribution of the statistical ensemble of given small quantum systems in the thermodynamical equilibrium with (macroscopic) black hole as thermal reservoir. We suggest that, practically, only the ground mass quantum state is significantly degenerate while all the other, excited mass quantum states, are non-degenerate. Kerr-Newman black hole entropy is practically equivalent to the ground mass quantum state degeneration. Given statistical distribution admits a rough (qualitative) but simple modeling of Hawking radiation of the black hole too.

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