scholarly journals Single-shot energetic-based estimator for entanglement in a half-parity measurement setup

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 166 ◽  
Author(s):  
Cyril Elouard ◽  
Alexia Auffèves ◽  
Géraldine Haack
Keyword(s):  
Information Technologies ◽  
Detection Efficiency ◽  
Quantum Correlations ◽  
Quantum Trajectory ◽  
Single Shot ◽  
Thermodynamic Quantities ◽  
The Road ◽  
Trajectory Approach ◽  
New Strategy ◽  
Parity Measurement

Producing and certifying entanglement between distant qubits is a highly desirable skill for quantum information technologies. Here we propose a new strategy to monitor and characterize entanglement genesis in a half parity measurement setup, that relies on the continuous readout of an energetic observable which is the half-parity observable itself. Based on a quantum-trajectory approach, we theoretically analyze the statistics of energetic fluctuations for a pair of continuously monitored qubits. We quantitatively relate these energetic fluctuations to the rate of entanglement produced between the qubits, and build an energetic-based estimator to assess the presence of entanglement in the circuit. Remarkably, this estimator is valid at the single-trajectory level and shows to be robust against finite detection efficiency. Our work paves the road towards a fundamental understanding of the stochastic energetic processes associated with entanglement genesis, and opens new perspectives for witnessing quantum correlations thanks to quantum thermodynamic quantities.

scholarly journals An analysis of reading out the state of a charge quantum bit

2003 ◽  
Vol 3 (2) ◽  
pp. 121-138
Author(s):  
H-S. Goan
Keyword(s):  
Density Matrix ◽  
Master Equation ◽  
The State ◽  
Qubit State ◽  
Reduced Density Matrix ◽  
Quantum Trajectory ◽  
Single Shot ◽  
Quantum Bit ◽  
Trajectory Approach ◽  
Reduced Density

We provide a unified picture for the master equation approach and the quantum trajectory approach to a measurement problem of a two-state quantum system (a qubit), an electron coherently tunneling between two coupled quantum dots (CQD's) measured by a low transparency point contact (PC) detector. We show that the master equation of ``partially'' reduced density matrix can be derived from the quantum trajectory equation (stochastic master equation) by simply taking a ``partial'' average over the all possible outcomes of the measurement. If a full ensemble average is taken, the traditional (unconditional) master equation of reduced density matrix is then obtained. This unified picture, in terms of averaging over (tracing out) different amount of detection records (detector states), for these seemingly different approaches reported in the literature is particularly easy to understand using our formalism. To further demonstrate this connection, we analyze an important ensemble quantity for an initial qubit state readout experiment, P(N,t), the probability distribution of finding N electron that have tunneled through the PC barrier(s) in time t. The simulation results of P(N,t) using 10000 quantum trajectories and corresponding measurement records are, as expected, in very good agreement with those obtained from the Fourier analysis of the ``partially'' reduced density matrix. However, the quantum trajectory approach provides more information and more physical insights into the ensemble and time averaged quantity P(N,t). Each quantum trajectory resembles a single history of the qubit state in a single run of the continuous measurement experiment. We finally discuss, in this approach, the possibility of reading out the state of the qubit system in a single-shot experiment.

Features of the Harvesting and Logging Equipment Market in Russia

2020 ◽  
pp. 132-147
Author(s):  
M.A. Piskunov ◽  
Keyword(s):  
Information Technologies ◽  
Import Substitution ◽  
Road Construction ◽  
Forest Sector ◽  
Specific Information ◽  
Service Network ◽  
Russian Market ◽  
The Road ◽  
Foreign Companies ◽  
Transnational Companies

Russian forest sector forms an attractive market for harvesting and logging equipment, however the position of Russian manufacturers is extremely weak. A brief overview of the current state of the market is presented with reference to the open sources. Its features are mentioned as compared to the road construction and agricultural machinery sectors. Three transnational companies dominate the Russian market of harvesting and logging equipment: John Deere, Ponsse and Komatsu. Most of the purchased equipment falls on machines for cut-tolength technology, such as harvester and forwarder. The market volume of new machines is estimated at 330–420 forwarders, 165–300 harvesters, about 30–40 feller bunchers and the same number of skidders. There were two waves in the consolidation of the position of foreign companies in Russia. The first was connected with the delivery of equipment and the development of foreign brands in Russia against the background of still high-profile positions of Russian manufacturers in the market. The second is the takeover of enterprises having a service network and reputation by diversified transnational corporations. The main strategies of the leading companies in the current situation are the export of equipment to Russia and the development of a service network. Companies do not turn to another level associated with the opening of production sites or joint ventures for the production of harvesting and logging machines. The Russian market is characterized by the absence of a strong Russian manufacturer of harvesting and logging machines, which is ready to significantly influence or actively participate in the processes of import substitution. The position of such a manufacturer is gradually occupied by the Belarusian Amkodor Holding. The purchase of new harvesting and logging machines can afford major timber companies. The main production sites of harvesting and logging machines are located in Finland, Sweden, USA, and Canada. In order to support forestry machine engineering, in addition to economic measures of stimulation approved in other sectors, it is proposed: to organize the work of scientific forest engineering centers on the base of public-private partnership with the financial support from the major vertically-integrated timber corporate groups; to stimulate the development of Russian sector-specific information technologies for harvesting and logging; to initiate the partnership with companies from the People’s Republic of China to launch the design and production of new-generation harvesting and logging machines.

scholarly journals Computing conditional entropies for quantum correlations

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peter Brown ◽  
Hamza Fawzi ◽  
Omar Fawzi
Keyword(s):  
Quantum Key Distribution ◽  
Detection Efficiency ◽  
Conditional Entropy ◽  
Key Distribution ◽  
Quantum Correlations ◽  
Upper Bounds ◽  
Cryptographic Protocols ◽  
Quantum States ◽  
Security Proofs

AbstractThe rates of quantum cryptographic protocols are usually expressed in terms of a conditional entropy minimized over a certain set of quantum states. In particular, in the device-independent setting, the minimization is over all the quantum states jointly held by the adversary and the parties that are consistent with the statistics that are seen by the parties. Here, we introduce a method to approximate such entropic quantities. Applied to the setting of device-independent randomness generation and quantum key distribution, we obtain improvements on protocol rates in various settings. In particular, we find new upper bounds on the minimal global detection efficiency required to perform device-independent quantum key distribution without additional preprocessing. Furthermore, we show that our construction can be readily combined with the entropy accumulation theorem in order to establish full finite-key security proofs for these protocols.

scholarly journals The quantum trajectory approach to quantum feedback control of an oscillator revisited

2012 ◽  
Vol 370 (1979) ◽  
pp. 5338-5353 ◽  
Author(s):  
Andrew C. Doherty ◽  
A. Szorkovszky ◽  
G. I. Harris ◽  
W. P. Bowen
Keyword(s):  
Master Equation ◽  
Quantum Trajectory ◽  
Measurement Sensitivity ◽  
Position Measurement ◽  
Stochastic Master Equation ◽  
Trajectory Approach ◽  
Quantum Feedback ◽  
Master Equation Approach ◽  
Rotating Wave ◽  
Parametric Driving

We revisit the stochastic master equation approach to feedback cooling of a quantum mechanical oscillator undergoing position measurement. By introducing a rotating wave approximation for the measurement and bath coupling, we can provide a more intuitive analysis of the achievable cooling in various regimes of measurement sensitivity and temperature. We also discuss explicitly the effect of backaction noise on the characteristics of the optimal feedback. The resulting rotating wave master equation has found application in our recent work on squeezing the oscillator motion using parametric driving and may have wider interest.

THE QUANTUM TRAJECTORY APPROACH TO GEOMETRIC PHASE FOR OPEN SYSTEMS

2005 ◽  
Vol 20 (22) ◽  
pp. 1635-1654 ◽  
Author(s):  
ANGELO CAROLLO
Keyword(s):  
Quantum System ◽  
Open System ◽  
Geometric Phase ◽  
Open Systems ◽  
Quantum Trajectory ◽  
Operational Method ◽  
Markovian Approximation ◽  
Physical Systems ◽  
Quantum Jump ◽  
Trajectory Approach

The quantum jump method for the calculation of geometric phase is reviewed. This is an operational method to associate a geometric phase to the evolution of a quantum system subjected to decoherence in an open system. The method is general and can be applied to many different physical systems, within the Markovian approximation. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. It is shown that the geometric phase is to very large extent insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.

scholarly journals Adapting the drivers to the road: a new strategy for cancer evolution?

2015 ◽  
Vol 26 (5) ◽  
pp. 827-829 ◽  
Author(s):  
M. Touat ◽  
F. Dhermain ◽  
F. André ◽  
M. Sanson
Keyword(s):  
Cancer Evolution ◽  
The Road ◽  
New Strategy

scholarly journals ARE QUANTUM CORRELATIONS GENUINELY QUANTUM?

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345016 ◽  
Author(s):  
ANTONIO DI LORENZO
Keyword(s):  
Detection Efficiency ◽  
Hidden Variables ◽  
Random Variables ◽  
Quantum Correlations ◽  
Random Mechanism ◽  
Spin Singlet ◽  
Action At A Distance ◽  
Probability Decomposition

It is shown that the probabilities for the spin singlet can be reproduced through classical resources, with no communication between the distant parties, by using merely shared (pseudo-)randomness. If the parties are conscious beings aware of both the hidden-variables and the random mechanism, then one has a conspiracy. If the parties are aware of only the random variables, they may be induced to believe that they are able to send instantaneous information to one another. It is also possible to reproduce the correlations at the price of reducing the detection efficiency. It is further demonstrated that the same probability decomposition could be realized through action-at-a-distance, provided it existed.

Trapping states and micromaser dynamics by a quantum-trajectory approach

1998 ◽  
Vol 151 (4-6) ◽  
pp. 395-405 ◽  
Author(s):  
F. Casagrande ◽  
M. Garavaglia ◽  
A. Lulli
Keyword(s):  
Quantum Trajectory ◽  
Trajectory Approach

scholarly journals INDICATORS OF THE ACTIVITIES OF THE CUSTOMS BODIES OF THE RUSSIAN FEDERATION IN THE CONTEXT OF IMPLEMENTING THE CONCEPT "TEN STEPS TOWARDS BUSINESS"

2018 ◽  
pp. 12-16 ◽  
Author(s):  
A. D. Skudarnova ◽  
D. D. Razhivina
Keyword(s):  
Comparative Analysis ◽  
Russian Federation ◽  
Economic Activity ◽  
Information Technologies ◽  
The Road ◽  
Road Map ◽  
The Russian Federation ◽  
Modern Information ◽  
Key Indicators

The article is devoted to the problems of interaction between customs authorities and participants in foreign economic activity, ways of developing the customs system and supporting business through the introduction of modern information technologies, a comparative analysis of key indicators of assessing the quality of customs services in accordance with the road map " 10 steps towards the business "and the indicators presented in the existing system for assessing the performance of customs bodies of Russia Federation.

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