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The Spectral Excess Theorem (SPET) for distance-regular graphs states that a regular (connected) graph is distance-regular if and only if its spectral-excess equals its average excess. Recently, some local or global approaches to the SPET…

Spectral Theory · Mathematics 2012-05-29 M. A. Fiol

A continuous quantum walk on a graph $X$ with adjacency matrix $A$ is specified by the 1-parameter family of unitary matrices $U(t)=\exp(itA)$. These matrices act on the state space of a quantum system, the states of which we may represent…

Combinatorics · Mathematics 2017-10-12 Chris Godsil

We present a protocol for quantum state transfer and remote state preparation across spin chains which operate in their anti-ferromagnetic mode. The proposed mechanism harnesses the inherent entanglement of the ground state of the strongly…

Strongly Correlated Electrons · Physics 2014-07-30 Sima Pouyandeh , Farhad Shahbazi , Abolfazl Bayat

We present a numerical method based on real-space renormalization that outputs the exact ground space of "frustration-free" Hamiltonians. The complexity of our method is polynomial in the degeneracy of the ground spaces of the Hamiltonians…

Strongly Correlated Electrons · Physics 2013-09-23 Adrian E. Feiguin , Rolando D. Somma , Cristian D. Batista

Perfect state transfer is possible in modulated spin chains, imperfections however are likely to corrupt the state transfer. We study the robustness of this quantum communication protocol in the presence of disorder both in the exchange…

Quantum Physics · Physics 2007-05-23 Gabriele De Chiara , Davide Rossini , Simone Montangero , Rosario Fazio

We show how to achieve perfect quantum state transfer and construct effective two-qubit gates between distant sites in engineered bosonic and fermionic networks. The Hamiltonian for the system can be determined by choosing an eigenvalue…

Quantum Physics · Physics 2009-11-10 Man-Hong Yung , Sougato Bose

We generalise Spatial Transformer Networks (STN) by replacing the parametric transformation of a fixed, regular sampling grid with a deformable, statistical shape model which is itself learnt. We call this a Statistical Transformer Network…

Computer Vision and Pattern Recognition · Computer Science 2018-04-20 Anil Bas , William A. P. Smith

We consider a system of static spin qubits embedded in a one-dimensional spin coherent channel and develop a scheme to readout the state of one and two qubits separately. We use unpolarized flying qubits for this purpose that scatter off…

Quantum Physics · Physics 2021-06-02 Amritesh Sharma , Ashwin A. Tulapurkar

We prove that estimating the ground state energy of a translationally-invariant, nearest-neighbour Hamiltonian on a 1D spin chain is QMAEXP-complete, even for systems of low local dimension (roughly 40). This is an improvement over the best…

Quantum Physics · Physics 2017-11-15 Johannes Bausch , Toby Cubitt , Maris Ozols

In this work, we use the Hamiltonian of a modified Dzyaloshinskii-Moriya model and investigate the perfect transfer of the quantum state on the spin networks. In this paper, we calculate fidelity in which fidelity depends on magnetic field…

Quantum Physics · Physics 2010-10-04 S. Salimi , B. Ghavami , Arash Sorouri

We suggest a scheme that allows arbitrarily perfect state transfer even in the presence of random fluctuations in the couplings of a quantum chain. The scheme performs well for both spatially correlated and uncorrelated fluctuations if they…

Quantum Physics · Physics 2007-05-23 Daniel Burgarth , Sougato Bose

Recent work have shown how the optimal state-feedback, obtained as the solution to the Hamilton-Jacobi-Bellman equations, can be approximated for several nonlinear, deterministic systems by deep neural networks. When imitation (supervised)…

Neural and Evolutionary Computing · Computer Science 2019-04-02 Dario Izzo , Dharmesh Tailor , Thomas Vasileiou

When the coefficients of the cubic terms match the coefficients in the boundary conditions at a vertex of a star graph and satisfy a certain constraint, the nonlinear Schr\"{o}dinger (NLS) equation on the star graph can be transformed to…

Analysis of PDEs · Mathematics 2019-02-12 Adilbek Kairzhan , Dmitry E. Pelinovsky , Roy H. Goodman

A bipartite spin system is proposed for which a fast transfer from one defined state into another exists. For sufficient coupling between the spins, this implements a bit-flipping mechanism which is much faster than that induced by…

Quantum Physics · Physics 2023-10-17 Maximilian F. I. Kieler , Arnd Bäcker

A simple method for transmitting quantum states within a quantum computer is via a quantum spin chain---that is, a path on $n$ vertices. Unweighted paths are of limited use, and so a natural generalization is to consider weighted paths;…

Quantum Physics · Physics 2019-03-26 Steve Kirkland , Darian McLaren , Rajesh Pereira , Sarah Plosker , Xiaohong Zhang

The XX model with uniform couplings represents the most natural choice for quantum state transfer through spin chains. Given that it has long been established that single-qubit states cannot be transferred with perfect fidelity in this…

Quantum Physics · Physics 2014-12-04 Rúben Sousa , Yasser Omar

Based on shortcuts to adiabaticity and quantum Zeno dynamics, we present a protocol to implement quantum state transfer (QST) in a quantum spin-1/2 chain. In the protocol, the complex Hamiltonian of an $N$-site system is simplified, and a…

Quantum Physics · Physics 2018-02-14 Bi-Hua Huang , Yi-Hao Kang , Ye-Hong Chen , Zhi-Cheng Shi , Jie Song , Yan Xia

We consider the perfect transfer of a state between arbitrary nodes of one-dimensional spin-1/2 chain with optimally engineered couplings. Motivated by the fact that such a system could be used as a data bus for connecting multiple quantum…

Quantum Physics · Physics 2019-03-06 N. E. Palaiodimopoulos , I. Brouzos , N. Georgoulea , P. A. Kalozoumis , F. K. Diakonos

We study a quantum state transfer between spins interacting with an arbitrary network of spins coupled by uniform XX interactions. It is shown that in such a system under fairly general conditions, we can expect a nearly perfect transfer of…

Quantum Physics · Physics 2015-06-26 A. Wojcik , T. Luczak , P. Kurzynski , A. Grudka , T. Gdala , M. Bednarska

In this paper, we investigate a high-dimensional quantum state transfer protocol. An arbitrary unknown high-dimensional state can be transferred with high fidelity between two remote registers through a XX coupling spin chain of arbitrary…

Quantum Physics · Physics 2013-04-29 Wei Qin , Chuan Wang , Gui-Lu Long