Feedback control for communication with non-orthogonal states

2007 ◽  
Vol 7 (1&2) ◽  
pp. 127-138
Author(s):  
K. Jacobs
Keyword(s):  
Feedback Control ◽  
Quantum System ◽  
Continuous Measurement ◽  
Information Gain ◽  
Quantum Mechanical ◽  
Optimal Measurement ◽  
Classical Information ◽  
Long Time ◽  
Initial Preparation ◽  
Initial States

Communicating classical information with a quantum system involves the receiver making a measurement on the system so as to distinguish as well as possible the alphabet of states used by the sender. We consider the situation in which this measurement takes an appreciable time. In this case the measurement must be described by a continuous measurement process. We consider a continuous implementation of the optimal measurement for distinguishing between two non-orthogonal states, and show that feedback control can be used during this measurement to increase the rate at which the information regarding the initial preparation is obtained. We show that while the maximum obtainable increase is modest, the effect is purely quantum mechanical in the sense that the enhancement is only possible when the initial states are non-orthogonal. We find further that the enhancement in the rate of information gain is achieved at the expense of reducing the total information which the measurement can extract in the long-time limit.

scholarly journals Process Emulation System for High-Power Piezoelectric Ultrasonic Actuators

2015 ◽  
Vol 2 (3-4) ◽  
pp. 201-205
Author(s):  
Igor Ille ◽  
Sebastian Mojrzisch ◽  
Jens Twiefel
Keyword(s):  
Feedback Control ◽  
Low Cost ◽  
Stable Process ◽  
Present System ◽  
Wide Field ◽  
Hardware In The Loop ◽  
Ultrasonic Assisted ◽  
Long Time ◽  
Number Of Cycles ◽  
High Flexibility

Abstract Ultrasonic actuators are used for a wide field of applications. The vibration energy can be used to realize many processes like ultrasonic welding or bonding. Furthermore there are many processes which run more efficient and faster combined with ultrasonic vibration like ultrasonic-assisted turning or drilling. Piezoelectric transducers are the main part of those applications. Most of the applications have a time-variant load behavior and need an amplitude feedback control to guarantee a stable process. To ensure correct function tests of the feedback control systems have to be done. In this case the processes have to be executed in association with a high number of cycles. To emulate the behavior of the environment the automotive and aerospace industries use hardware in the loop systems since a long time but there is no such a method for ultrasonic systems. This paper presents a method to realize high dynamic load emulation for different ultrasonic applications. Using a piezoelectric transformer it is possible to reproduce load curves by active damping on the secondary side of the transformer using a current proportional digital feedback circuit. A theoretical and experimental study of hardware in the loop system for ultrasonic applications is given by this paper. The present system allows testing a wide field of feedback control algorithms with high flexibility and a high number of cycles by utilization of low-cost components. This proceeding decreases design periods in association with feedback control.

scholarly journals On estimation and feedback control of spin-1/2 systems with unknown initial states

2020 ◽  
Vol 53 (2) ◽  
pp. 5863-5868
Author(s):  
Weichao Liang ◽  
Nina H. Amini ◽  
Paolo Mason
Keyword(s):  
Feedback Control ◽  
Initial States

Quantum universality by state distillationIndirect quantum control for finite-dimensional coupled systems

2010 ◽  
Vol 10 (1&2) ◽  
pp. 87-96
Author(s):  
J. Nie ◽  
H.C. Fu ◽  
X.X. Yi
Keyword(s):  
Quantum System ◽  
Quantum Control ◽  
Coherent Control ◽  
Coupled Systems ◽  
Preparation Technology ◽  
State Preparation ◽  
Finite Dimensional ◽  
State Dependent ◽  
Control Scheme ◽  
Initial States

We present a new analysis on the quantum control for a quantum system coupled to a quantum probe. This analysis is based on the coherent control for the quantum system and a hypothesis that the probe can be prepared in specified initial states. The results show that a quantum system can be manipulated by probe state-dependent coherent control. In this sense, the present analysis provides a new control scheme which combines the coherent control and state preparation technology.

scholarly journals USE OF THE WHIRLIGIG PRINCIPLE FOR STABILIZING THE INITIAL STATES OF SOME CLASSIC AND QUANTUM SYSTEMS

2020 ◽  
pp. 78-81
Author(s):  
V.A. Buts
Keyword(s):  
Quantum System ◽  
Excited States ◽  
Quantum Systems ◽  
Nuclear Systems ◽  
Initial States

It is shown that the whirligig principle can be used for stabilization of the initial states of some classical and quantum systems. This feature of the whirligig principle is demonstrated by simple examples. The most important result of this work is the proof of the fact that the stabilization of the excited states of quantum systems can be realized by acting not on the quantum system itself, but by acting on the states into which the system must go. Potentially, this result can be used to stabilize excited nuclear systems.

Error correction of quantum system dynamics via measurement–feedback control

2019 ◽  
Vol 52 (16) ◽  
pp. 165501
Author(s):  
Du Ran ◽  
Zhi-Cheng Shi ◽  
Zhen-Biao Yang ◽  
Jie Song ◽  
Yan Xia
Keyword(s):  
Feedback Control ◽  
System Dynamics ◽  
Error Correction ◽  
Quantum System ◽  
Measurement Feedback

LIMITATION ON THE ACCESSIBLE INFORMATION FOR QUANTUM CHANNELS WITH INEFFICIENT MEASUREMENTS

2005 ◽  
Vol 03 (supp01) ◽  
pp. 87-95
Author(s):  
KURT JACOBS
Keyword(s):  
Quantum System ◽  
Von Neumann Entropy ◽  
Quantum Channels ◽  
Initial State ◽  
Von Neumann ◽  
Classical Information ◽  
Quantum Operations ◽  
Amount Of Information ◽  
Accessible Information

To transmit classical information using a quantum system, the sender prepares the system in one of a set of possible states and sends it to the receiver. The receiver then makes a measurement on the system to obtain information about the senders choice of state. The amount of information which is accessible to the receiver depends upon the encoding and the measurement. Here we derive a bound on this information which generalizes the bound derived by Schumacher, Westmoreland and Wootters [Schumacher, Westmoreland and Wootters, Phys. Rev. Lett. 76, 3452 (1996)] to include inefficient measurements, and thus all quantum operations. This also allows us to obtain a generalization of a bound derived by Hall [Hall, Phys. Rev. A 55, 100 (1997)], and to show that the average reduction in the von Neumann entropy which accompanies a measurement is concave in the initial state, for all quantum operations.

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