scholarly journals Hybrid quantum circuits: Superconducting circuits interacting with other quantum systems

2013 ◽  
Vol 85 (2) ◽  
pp. 623-653 ◽  
Author(s):  
Ze-Liang Xiang ◽  
Sahel Ashhab ◽  
J. Q. You ◽  
Franco Nori
Keyword(s):  
Quantum Systems ◽  
Quantum Circuits ◽  
Superconducting Circuits

scholarly journals Advanced exact synthesis of Clifford+T circuits

2020 ◽  
Vol 19 (9) ◽  
Author(s):  
Philipp Niemann ◽  
Robert Wille ◽  
Rolf Drechsler
Keyword(s):  
Large Scale ◽  
Fault Tolerant ◽  
Logic Synthesis ◽  
Research Problem ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Research Attention ◽  
Small Quantum ◽  
Significant Research ◽  
Important Research Problem

Abstract Quantum systems provide a new way of conducting computations based on the so-called qubits. Due to the potential for significant speed-ups, this field received significant research attention in recent years. The Clifford+T library is a very promising and popular gate library for these kinds of computations. Unlike other libraries considered so far, it consists of only a small number of gates for all of which robust, fault-tolerant realizations are known for many technologies that seem to be promising for large-scale quantum computing. As a consequence, (logic) synthesis of Clifford+T quantum circuits became an important research problem. However, previous work in this area has several drawbacks: Corresponding approaches are either only applicable to very small quantum systems or lead to circuits that are far from being optimal. The latter is mainly caused by the fact that current synthesis realizes the desired circuit by a local, i.e., column-wise, consideration of the underlying unitary transformation matrix to be synthesized. In this paper, we analyze the conceptual drawbacks of this approach and propose to overcome them by taking a global view of the matrices and perform a separation of concerns regarding individual synthesis steps. We precisely describe a corresponding algorithm as well as its efficient implementation on top of decision diagrams. Experimental results confirm the resulting benefits and show improvements of up to several orders of magnitudes in costs compared to previous work.

scholarly journals Quantum circuits for strongly correlated quantum systems

2009 ◽  
Vol 79 (3) ◽  
Author(s):  
Frank Verstraete ◽  
J. Ignacio Cirac ◽  
José I. Latorre
Keyword(s):  
Quantum Systems ◽  
Quantum Circuits ◽  
Strongly Correlated ◽  
Correlated Quantum Systems

scholarly journals An efficient quantum algorithm for the time evolution of parameterized circuits

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 512
Author(s):  
Stefano Barison ◽  
Filippo Vicentini ◽  
Giuseppe Carleo
Keyword(s):  
Variational Principle ◽  
Time Evolution ◽  
Quantum Dynamics ◽  
Quantum Algorithm ◽  
Quantum Systems ◽  
Small Time ◽  
Quantum Circuits ◽  
Time Step ◽  
Optimal Linear ◽  
Global Nature

We introduce a novel hybrid algorithm to simulate the real-time evolution of quantum systems using parameterized quantum circuits. The method, named "projected – Variational Quantum Dynamics" (p-VQD) realizes an iterative, global projection of the exact time evolution onto the parameterized manifold. In the small time-step limit, this is equivalent to the McLachlan's variational principle. Our approach is efficient in the sense that it exhibits an optimal linear scaling with the total number of variational parameters. Furthermore, it is global in the sense that it uses the variational principle to optimize all parameters at once. The global nature of our approach then significantly extends the scope of existing efficient variational methods, that instead typically rely on the iterative optimization of a restricted subset of variational parameters. Through numerical experiments, we also show that our approach is particularly advantageous over existing global optimization algorithms based on the time-dependent variational principle that, due to a demanding quadratic scaling with parameter numbers, are unsuitable for large parameterized quantum circuits.

scholarly journals Laser-annealing Josephson junctions for yielding scaled-up superconducting quantum processors

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jared B. Hertzberg ◽  
Eric J. Zhang ◽  
Sami Rosenblatt ◽  
Easwar Magesan ◽  
John A. Smolin ◽  
...  
Keyword(s):  
Statistical Modeling ◽  
Josephson Junctions ◽  
Laser Annealing ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Fixed Frequency ◽  
Superconducting Quantum Circuits

AbstractAs superconducting quantum circuits scale to larger sizes, the problem of frequency crowding proves a formidable task. Here we present a solution for this problem in fixed-frequency qubit architectures. By systematically adjusting qubit frequencies post-fabrication, we show a nearly tenfold improvement in the precision of setting qubit frequencies. To assess scalability, we identify the types of “frequency collisions” that will impair a transmon qubit and cross-resonance gate architecture. Using statistical modeling, we compute the probability of evading all such conditions, as a function of qubit frequency precision. We find that, without post-fabrication tuning, the probability of finding a workable lattice quickly approaches 0. However, with the demonstrated precisions it is possible to find collision-free lattices with favorable yield. These techniques and models are currently employed in available quantum systems and will be indispensable as systems continue to scale to larger sizes.

scholarly journals Fisher Information in Noisy Intermediate-Scale Quantum Applications

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 539
Author(s):  
Johannes Jakob Meyer
Keyword(s):  
Fisher Information ◽  
Quantum Algorithms ◽  
Quantum Fisher Information ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Quantum Computers ◽  
Quantum Devices ◽  
Intermediate Scale ◽  
Quantum Sensing ◽  
Near Term

The recent advent of noisy intermediate-scale quantum devices, especially near-term quantum computers, has sparked extensive research efforts concerned with their possible applications. At the forefront of the considered approaches are variational methods that use parametrized quantum circuits. The classical and quantum Fisher information are firmly rooted in the field of quantum sensing and have proven to be versatile tools to study such parametrized quantum systems. Their utility in the study of other applications of noisy intermediate-scale quantum devices, however, has only been discovered recently. Hoping to stimulate more such applications, this article aims to further popularize classical and quantum Fisher information as useful tools for near-term applications beyond quantum sensing. We start with a tutorial that builds an intuitive understanding of classical and quantum Fisher information and outlines how both quantities can be calculated on near-term devices. We also elucidate their relationship and how they are influenced by noise processes. Next, we give an overview of the core results of the quantum sensing literature and proceed to a comprehensive review of recent applications in variational quantum algorithms and quantum machine learning.

scholarly journals Complexity from the reduced density matrix: a new diagnostic for chaos

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Arpan Bhattacharyya ◽  
S. Shajidul Haque ◽  
Eugene H. Kim
Keyword(s):  
Density Matrix ◽  
Quantum Chaos ◽  
Open Quantum Systems ◽  
Circuit Complexity ◽  
Quantum Systems ◽  
Harmonic Oscillators ◽  
Quantum Circuits ◽  
Reduced Density Matrix ◽  
Evolution Of Complexity ◽  
Reduced Density

Abstract We investigate circuit complexity to characterize chaos in multiparticle quantum systems. In the process, we take a stride to analyze open quantum systems by using complexity. We propose a new diagnostic of quantum chaos from complexity based on the reduced density matrix by exploring different types of quantum circuits. Through explicit calculations on a toy model of two coupled harmonic oscillators, where one or both of the oscillators are inverted, we demonstrate that the evolution of complexity is a possible diagnostic of chaos.

A LOGIC FOR QUANTUM COMPUTATION AND CLASSICAL SIMULATION OF QUANTUM ALGORITHMS

2008 ◽  
Vol 06 (02) ◽  
pp. 255-280
Author(s):  
M. K. PATRA
Keyword(s):  
Quantum Computation ◽  
General Formula ◽  
Quantum Algorithms ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Finite Dimensional ◽  
Classical Simulation ◽  
Complex Extension

The semantics of a language for reasoning about finite-dimensional quantum systems is presented. This language can express most important classes of assertions about quantum systems, including formulas for outputs of all combinational quantum circuits/algorithms. The main result of this paper is an algorithm for efficient translation of a formula of language into an equivalent formula in another decidable language ℝℂ, which is the language of reals and its complex extension. An important consequence is a descriptive characterization of quantum circuits that can be efficiently simulated classically. We illustrate this with examples of two classes of quantum circuits which are known to have efficient classical simulation. The algorithm for deciding the satisfiability of a general formula can be adapted for the simulation.

scholarly journals An FPGA-Based Quantum Computing Emulation Framework Based on Serial-Parallel Architecture

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Y. H. Lee ◽  
M. Khalil-Hani ◽  
M. N. Marsono
Keyword(s):  
Processing Speed ◽  
Large Scale ◽  
Quantum Algorithms ◽  
Parallel Architecture ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Proof Of Concept ◽  
Hardware Emulation ◽  
Field Programmable ◽  
Speed Up

Hardware emulation of quantum systems can mimic more efficiently the parallel behaviour of quantum computations, thus allowing higher processing speed-up than software simulations. In this paper, an efficient hardware emulation method that employs a serial-parallel hardware architecture targeted for field programmable gate array (FPGA) is proposed. Quantum Fourier transform and Grover’s search are chosen as case studies in this work since they are the core of many useful quantum algorithms. Experimental work shows that, with the proposed emulation architecture, a linear reduction in resource utilization is attained against the pipeline implementations proposed in prior works. The proposed work contributes to the formulation of a proof-of-concept baseline FPGA emulation framework with optimization on datapath designs that can be extended to emulate practical large-scale quantum circuits.

Single-Shot Correlations and Two-Qubit Gate of Solid-State Spins

Science ◽  
2011 ◽  
Vol 333 (6047) ◽  
pp. 1269-1272 ◽  
Author(s):  
K. C. Nowack ◽  
M. Shafiei ◽  
M. Laforest ◽  
G. E. D. K. Prawiroatmodjo ◽  
L. R. Schreiber ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Quantum Information Processing ◽  
Quantum Systems ◽  
Quantum Circuits ◽  
Double Quantum ◽  
Single Shot ◽  
Complete Set ◽  
Single Quantum Dot ◽  
Qubit Gate

Measurement of coupled quantum systems plays a central role in quantum information processing. We have realized independent single-shot read-out of two electron spins in a double quantum dot. The read-out method is all-electrical, cross-talk between the two measurements is negligible, and read-out fidelities are ~86% on average. This allows us to directly probe the anticorrelations between two spins prepared in a singlet state and to demonstrate the operation of the two-qubit exchange gate on a complete set of basis states. The results provide a possible route to the realization and efficient characterization of multiqubit quantum circuits based on single quantum dot spins.

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