scholarly journals Coherence and Entanglement Dynamics in Training Variational Quantum Perceptron

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1277
Author(s):  
Min Namkung ◽  
Younghun Kwon
Keyword(s):  
Quantum Computation ◽  
Quantum Coherence ◽  
Quantum Algorithms ◽  
Total System ◽  
Entanglement Dynamics ◽  
Grover Algorithm

In quantum computation, what contributes supremacy of quantum computation? One of the candidates is known to be a quantum coherence because it is a resource used in the various quantum algorithms. We reveal that quantum coherence contributes to the training of variational quantum perceptron proposed by Y. Du et al., arXiv:1809.06056 (2018). In detail, we show that in the first part of the training of the variational quantum perceptron, the quantum coherence of the total system is concentrated in the index register and in the second part, the Grover algorithm consumes the quantum coherence in the index register. This implies that the quantum coherence distribution and the quantum coherence depletion are required in the training of variational quantum perceptron. In addition, we investigate the behavior of entanglement during the training of variational quantum perceptron. We show that the bipartite concurrence between feature and index register decreases since Grover operation is only performed on the index register. Also, we reveal that the concurrence between the two qubits of index register increases as the variational quantum perceptron is trained.

Engineering Electronic Structure to Protect Phase Memory in Molecular Qubits by Minimising Orbital Angular Momentum

2018 ◽  
Author(s):  
Ana Maria Ariciu ◽  
David H. Woen ◽  
Daniel N. Huh ◽  
Lydia Nodaraki ◽  
Andreas Kostopoulos ◽  
...  
Keyword(s):  
Electron Spin ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Pulse Sequences ◽  
Grover Algorithm ◽  
Ligand Shell ◽  
Information Strategies ◽  
Spin Qubit ◽  
Molecular Spin ◽  
The Impact

Using electron spins within molecules for quantum information processing (QIP) was first proposed by Leuenberger and Loss (1), who showed how the Grover algorithm could be mapped onto a Mn12 cage (2). Since then several groups have examined two-level (S = ½) molecular spin systems as possible qubits (3-12). There has also been a report of the implementation of the Grover algorithm in a four-level molecular qudit (13). A major challenge is to protect the spin qubit from noise that causes loss of phase information; strategies to minimize the impact of noise on qubits can be categorized as corrective, reductive, or protective. Corrective approaches allow noise and correct for its impact on the qubit using advanced microwave pulse sequences (3). Reductive approaches reduce the noise by minimising the number of nearby nuclear spins (7-11), and increasing the rigidity of molecules to minimise the effect of vibrations (which can cause a fluctuating magnetic field via spin-orbit coupling) (9,11); this is essentially engineering the ligand shell surrounding the electron spin. A protective approach would seek to make the qubit less sensitive to noise: an example of the protective approach is the use of clock transitions to render spin states immune to magnetic fields at first order (12). Here we present a further protective method that would complement reductive and corrective approaches to enhancing quantum coherence in molecular qubits. The target is a molecular spin qubit with an effective 2S ground state: we achieve this with a family of divalent rare-earth molecules that have negligible magnetic anisotropy such that the isotropic nature of the electron spin renders the qubit markedly less sensitive to magnetic noise, allowing coherent spin manipulations even at room temperature. If combined with the other strategies, we believe this could lead to molecular qubits with substantial advantages over competing qubit proposals.<br>

scholarly journals Quantifying computational advantage of Grover’s algorithm with the trace speed

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Valentin Gebhart ◽  
Luca Pezzè ◽  
Augusto Smerzi
Keyword(s):  
Quantum Coherence ◽  
Search Algorithm ◽  
Quantum Algorithms ◽  
Physical Origin ◽  
Computational Advantage ◽  
Speed Up ◽  
Quantum Speed Up ◽  
Quantum Statistical ◽  
Grover’S Search Algorithm ◽  
General Physical

AbstractDespite intensive research, the physical origin of the speed-up offered by quantum algorithms remains mysterious. No general physical quantity, like, for instance, entanglement, can be singled out as the essential useful resource. Here we report a close connection between the trace speed and the quantum speed-up in Grover’s search algorithm implemented with pure and pseudo-pure states. For a noiseless algorithm, we find a one-to-one correspondence between the quantum speed-up and the polarization of the pseudo-pure state, which can be connected to a wide class of quantum statistical speeds. For time-dependent partial depolarization and for interrupted Grover searches, the speed-up is specifically bounded by the maximal trace speed that occurs during the algorithm operations. Our results quantify the quantum speed-up with a physical resource that is experimentally measurable and related to multipartite entanglement and quantum coherence.

Efficient linear optics quantum computation

2001 ◽  
Vol 1 (Special) ◽  
pp. 13-19
Author(s):  
G.J. Milburn ◽  
T. Ralph ◽  
A. White ◽  
E. Knill ◽  
R. Laflamme
Keyword(s):  
Quantum Computation ◽  
Single Photon ◽  
Quantum Algorithms ◽  
Optical Nonlinearities ◽  
Linear Optics ◽  
Optical Elements ◽  
Particle Detectors ◽  
Feed Forward ◽  
Single Electrons ◽  
Photon Source

Two qubit gates for photons are generally thought to require exotic materials with huge optical nonlinearities. We show here that, if we accept two qubit gates that only work conditionally, single photon sources, passive linear optics and particle detectors are sufficient for implementing reliable quantum algorithms. The conditional nature of the gates requires feed-forward from the detectors to the optical elements. Without feed forward, non-deterministic quantum computation is possible. We discuss one proposed single photon source based on the surface acoustic wave guiding of single electrons.

scholarly journals Diamond-based quantum technologies

Photoniques ◽  
2021 ◽  
pp. 44-48
Author(s):  
Toeno Van Der Sar ◽  
Tim Hugo Taminiau ◽  
Ronald Hanson
Keyword(s):  
Quantum Computation ◽  
Long Range ◽  
Quantum Coherence ◽  
Room Temperature ◽  
Science And Technology ◽  
Quantum Networks ◽  
Key Characteristics ◽  
Quantum Sensing ◽  
Quantum Science

Optically accessible spins associated with defects in diamond provide a versatile platform for quantum science and technology. These spins combine multiple key characteristics, including long quantum coherence times, operation up to room temperature, and the capability to create long-range entanglement links through photons. These unique properties have propelled spins in diamond to the forefront of quantum sensing, quantum computation and simulation, and quantum networks.

scholarly journals The Jones polynomial: quantum algorithms and applications in quantum complexity theory

2008 ◽  
Vol 8 (1&2) ◽  
pp. 147-180
Author(s):  
P. Wocjan ◽  
J. Yard
Keyword(s):  
Quantum Computation ◽  
Braid Group ◽  
Quantum Algorithms ◽  
Primitive Root ◽  
Jones Polynomial ◽  
Tutte Polynomial ◽  
Roots Of Unity ◽  
Complete Problems ◽  
Primitive Roots ◽  
Quantum Complexity

We analyze relationships between quantum computation and a family of generalizations of the Jones polynomial. Extending recent work by Aharonov et al., we give efficient quantum circuits for implementing the unitary Jones-Wenzl representations of the braid group. We use these to provide new quantum algorithms for approximately evaluating a family of specializations of the HOMFLYPT two-variable polynomial of trace closures of braids. We also give algorithms for approximating the Jones polynomial of a general class of closures of braids at roots of unity. Next we provide a self-contained proof of a result of Freedman et al.\ that any quantum computation can be replaced by an additive approximation of the Jones polynomial, evaluated at almost any primitive root of unity. Our proof encodes two-qubit unitaries into the rectangular representation of the eight-strand braid group. We then give QCMA-complete and PSPACE-complete problems which are based on braids. We conclude with direct proofs that evaluating the Jones polynomial of the plat closure at most primitive roots of unity is a \#P-hard problem, while learning its most significant bit is PP-hard, circumventing the usual route through the Tutte polynomial and graph coloring.

Quantum Algorithms

2021 ◽  
pp. 82-101
Author(s):  
Renata Wong ◽  
Amandeep Singh Bhatia
Keyword(s):  
Quantum Computing ◽  
Fault Tolerance ◽  
Quantum Computation ◽  
Quantum Computer ◽  
Quantum Algorithms ◽  
Computer Hardware ◽  
Quantum Mechanical ◽  
Computational Power ◽  
Quantum Devices ◽  
The Core

In the last two decades, the interest in quantum computation has increased significantly among research communities. Quantum computing is the field that investigates the computational power and other properties of computers on the basis of the underlying quantum-mechanical principles. The main purpose is to find quantum algorithms that are significantly faster than any existing classical algorithms solving the same problem. While the quantum computers currently freely available to wider public count no more than two dozens of qubits, and most recently developed quantum devices offer some 50-60 qubits, quantum computer hardware is expected to grow in terms of qubit counts, fault tolerance, and resistance to decoherence. The main objective of this chapter is to present an introduction to the core quantum computing algorithms developed thus far for the field of cryptography.

scholarly journals NONLINEAR SCHRÖDINGER EQUATION FOR QUANTUM COMPUTATION

2006 ◽  
Vol 20 (18) ◽  
pp. 1099-1106 ◽  
Author(s):  
M. CEMAL YALABIK
Keyword(s):  
Schrödinger Equation ◽  
Quantum System ◽  
Large Class ◽  
Quantum Computation ◽  
Nonlinear Schrödinger Equation ◽  
Schrodinger Equation ◽  
Quantum Algorithms ◽  
Nonlinear Schrodinger Equation ◽  
Time Development ◽  
Nonlinear Schrödinger

Utilization of a quantum system whose time-development is described by the nonlinear Schrödinger equation in the transformation of qubits would make it possible to construct quantum algorithms which would be useful in a large class of problems. An example of such a system for implementing the logical NOR operation is demonstrated.

scholarly journals Quantum algorithms for spin models and simulable gate sets for quantum computation

2009 ◽  
Vol 80 (5) ◽  
Author(s):  
M. Van den Nest ◽  
W. Dür ◽  
R. Raussendorf ◽  
H. J. Briegel
Keyword(s):  
Quantum Computation ◽  
Quantum Algorithms ◽  
Spin Models

Quantum algorithms in one-way quantum computation

2010 ◽  
Vol 108 (2) ◽  
pp. 282-287
Author(s):  
G. Vallone ◽  
F. De Martini ◽  
P. Mataloni
Keyword(s):  
Quantum Computation ◽  
Quantum Algorithms

scholarly journals Modular quantum computing and quantum-like devices

2021 ◽  
pp. 2150020
Author(s):  
R. Vilela Mendes
Keyword(s):  
Quantum Computing ◽  
Quantum Computation ◽  
Quantum Algorithms ◽  
The Other ◽  
Classical Systems ◽  
Evolution Parameter ◽  
Space Coordinate ◽  
The One ◽  
Classical Computer

The two essential ideas in this paper are, on the one hand, that a considerable amount of the power of quantum computation may be obtained by adding to a classical computer a few specialized quantum modules and on the other hand, that such modules may be constructed out of classical systems obeying quantum-like equations where a space coordinate is the evolution parameter (thus playing the role of time in the quantum algorithms).

Sign in / Sign up

Export Citation Format

Share Document