scholarly journals Robust coherent spin centers from stable azafullerene radicals entrapped in cycloparaphenylene rings

Nanoscale ◽  
2021 ◽  
Author(s):  
Yuri Tanuma ◽  
Anastasios Stergiou ◽  
Andreja Bužan Bobnar ◽  
Mattia Gaboardi ◽  
Jeremy Rio ◽  
...  
Keyword(s):  
Quantum Computing ◽  
Quantum Systems ◽  
Coherent Spin

Molecular entities with robust spin-1/2 are natural two-level quantum systems for realizing qubits and are key ingredients of emerging quantum technologies such as quantum computing. Here we show that robust...

THE TRAPPED-ION QUBIT: COHERENT CONTROL IN INFINITE-DIMENSIONAL QUANTUM SYSTEMS

2009 ◽  
Vol 24 (32) ◽  
pp. 2565-2578
Author(s):  
C. RANGAN
Keyword(s):  
Quantum Computing ◽  
Quantum System ◽  
Quantum Control ◽  
Coherent Control ◽  
Quantum Information Processing ◽  
Quantum Systems ◽  
Infinite Dimensional ◽  
Trapped Ion ◽  
Rich Variety ◽  
Control Research

Theories of quantum control have, until recently, made the assumption that the Hilbert space of a quantum system can be truncated to finite dimensions. Such truncations, which can be achieved for most quantum systems via bandwidth restrictions, have enabled the development of a rich variety of quantum control and optimal control schemes. Recent studies in quantum information processing have addressed the control of infinite-dimensional quantum systems such as the quantum states of a trapped-ion. Controllability in an infinite-dimensional quantum system is hard to prove with conventional methods, and infinite-dimensional systems provide unique challenges in designing control fields. In this paper, we will discuss the control of a popular system for quantum computing the trapped-ion qubit. This system, modeled by a spin-half particle coupled to a quantized harmonic oscillator, is an example for a surprisingly rich variety of control problems. We will show how this infinite-dimensional quantum system can be examined via the lens of the Finite Controllability Theorem, two-color STIRAP, the generalized Heisenberg system, etc. These results are important from the viewpoint of developing more efficient quantum control protocols, particularly in quantum computing systems. This work shows how one can expand the scope of quantum control research to beyond that of finite-dimensional quantum systems.

scholarly journals Using quantum computing to create efficient algorithms

2021 ◽  
Vol 2056 (1) ◽  
pp. 012059
Author(s):  
I N Balaba ◽  
G S Deryabina ◽  
I A Pinchuk ◽  
I V Sergeev ◽  
S B Zabelina
Keyword(s):  
Quantum Mechanics ◽  
Quantum Computing ◽  
Computational Model ◽  
Exponential Growth ◽  
Quantum Algorithms ◽  
Quantum Systems ◽  
Efficient Algorithms ◽  
Historical Overview ◽  
Computing Model ◽  
Computational Strategy

Abstract The article presents a historical overview of the development of the mathematical idea of a quantum computing model - a new computational strategy based on the postulates of quantum mechanics and having advantages over the traditional computational model based on the Turing machine; clarified the features of the operation of multi-qubit quantum systems, which ensure the creation of efficient algorithms; the principles of quantum computing are outlined and a number of efficient quantum algorithms are described that allow solving the problem of exponential growth of the complexity of certain problems.

scholarly journals Quantum computing and second quantization

2017 ◽  
Vol 26 (03) ◽  
pp. 1741006 ◽  
Author(s):  
Hanna Makaruk
Keyword(s):  
Quantum Computing ◽  
Approximate Method ◽  
Quantum Systems ◽  
General Idea ◽  
Entangled States ◽  
Quantum Computers ◽  
Second Quantization ◽  
Particle Arrangement ◽  
The Many

Quantum computers by their nature are many particle quantum systems. Both the many-particle arrangement and being quantum are necessary for the existence of the entangled states, which are responsible for the parallelism of the quantum computers. Second quantization is a very important approximate method of describing such systems. This lecture will present the general idea of the second quantization, and discuss shortly some of the most important formulations of second quantization.

scholarly journals QInfer: Statistical inference software for quantum applications

Quantum ◽  
2017 ◽  
Vol 1 ◽  
pp. 5 ◽  
Author(s):  
Christopher Granade ◽  
Christopher Ferrie ◽  
Ian Hincks ◽  
Steven Casagrande ◽  
Thomas Alexander ◽  
...  
Keyword(s):  
Experimental Data ◽  
Quantum Computing ◽  
Statistical Analysis ◽  
Open Source ◽  
Quantum Systems ◽  
Post Processing ◽  
Experimental Protocols ◽  
Quantum Technology ◽  
Reproducible Manner ◽  
Analyze Data

Characterizing quantum systems through experimental data is critical to applications as diverse as metrology and quantum computing. Analyzing this experimental data in a robust and reproducible manner is made challenging, however, by the lack of readily-available software for performing principled statistical analysis. We improve the robustness and reproducibility of characterization by introducing an open-source library, QInfer, to address this need. Our library makes it easy to analyze data from tomography, randomized benchmarking, and Hamiltonian learning experiments either in post-processing, or online as data is acquired. QInfer also provides functionality for predicting the performance of proposed experimental protocols from simulated runs. By delivering easy-to-use characterization tools based on principled statistical analysis, QInfer helps address many outstanding challenges facing quantum technology.

Improved quantum ternary arithmetic

2016 ◽  
Vol 16 (9&10) ◽  
pp. 862-884
Author(s):  
Alex Bocharov ◽  
Shawn X. Cui ◽  
Martin Roetteler ◽  
Krysta M. Svore
Keyword(s):  
Quantum Computing ◽  
Finite Field ◽  
Quantum Systems ◽  
Arithmetic Circuits ◽  
Levels Of Abstraction ◽  
Circuit Depth

Qutrit (or ternary) structures arise naturally in many quantum systems, notably in certain non-abelian anyon systems. We present efficient circuits for ternary reversible and quantum arithmetics. Our main result is the derivation of circuits for two families of ternary quantum adders. The main distinction from the binary adders is a richer ternary carry which leads potentially to higher resource counts in universal ternary bases. Our ternary ripple adder circuit has a circuit depth of O(n) and uses only 1 ancilla, making it more efficient in both, circuit depth and width, when compared with previous constructions. Our ternary carry lookahead circuit has a circuit depth of only O(log n), while using O(n) ancillas. Our approach works on two levels of abstraction: at the first level, descriptions of arithmetic circuits are given in terms of gates sequences that use various types of non-Clifford reflections. At the second level, we break down these reflections further by deriving them either from the two-qutrit Clifford gates and the non-Clifford gate C(X) : |i, ji 7→ |i, j + δi,2 mod 3i or from the two-qutrit Clifford gates and the non-Clifford gate P9 = diag(e −2π i/9 , 1, e 2π i/9 ). The two choices of elementary gate sets correspond to two possible mappings onto two different prospective quantum computing architectures which we call the metaplectic and the supermetaplectic basis, respectively. Finally, we develop a method to factor diagonal unitaries using multi-variate polynomials over the ternary finite field which allows to characterize classes of gates that can be implemented exactly over the supermetaplectic basis.

scholarly journals New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alexander P. M. Place ◽  
Lila V. H. Rodgers ◽  
Pranav Mundada ◽  
Basil M. Smitham ◽  
Mattias Fitzpatrick ◽  
...  
Keyword(s):  
Quantum Computing ◽  
Quantum Systems ◽  
Two Dimensional ◽  
Dynamical Decoupling ◽  
Bulk Properties ◽  
New Material ◽  
Science Building ◽  
Quantum Science ◽  
The Way

AbstractThe superconducting transmon qubit is a leading platform for quantum computing and quantum science. Building large, useful quantum systems based on transmon qubits will require significant improvements in qubit relaxation and coherence times, which are orders of magnitude shorter than limits imposed by bulk properties of the constituent materials. This indicates that relaxation likely originates from uncontrolled surfaces, interfaces, and contaminants. Previous efforts to improve qubit lifetimes have focused primarily on designs that minimize contributions from surfaces. However, significant improvements in the lifetime of two-dimensional transmon qubits have remained elusive for several years. Here, we fabricate two-dimensional transmon qubits that have both lifetimes and coherence times with dynamical decoupling exceeding 0.3 milliseconds by replacing niobium with tantalum in the device. We have observed increased lifetimes for seventeen devices, indicating that these material improvements are robust, paving the way for higher gate fidelities in multi-qubit processors.

scholarly journals Dynamical Localization Simulated on Actual Quantum Hardware

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 654
Author(s):  
Andrea Pizzamiglio ◽  
Su Yeon Chang ◽  
Maria Bondani ◽  
Simone Montangero ◽  
Dario Gerace ◽  
...  
Keyword(s):  
Quantum Computing ◽  
Quantum Systems ◽  
Dynamical Localization ◽  
Small Scale ◽  
Quantum Computers ◽  
Convenient Tool ◽  
Highly Sensitive

Quantum computers are invaluable tools to explore the properties of complex quantum systems. We show that dynamical localization of the quantum sawtooth map, a highly sensitive quantum coherent phenomenon, can be simulated on actual, small-scale quantum processors. Our results demonstrate that quantum computing of dynamical localization may become a convenient tool for evaluating advances in quantum hardware performances.

REVERSIBLE VITERBI ALGORITHM AND ITS CLOSED-SYSTEM Q-DOMAIN CIRCUIT DESIGN AND COMPUTATION

2009 ◽  
Vol 18 (08) ◽  
pp. 1627-1649 ◽  
Author(s):  
ANAS N. AL-RABADI
Keyword(s):  
Quantum Computing ◽  
Circuit Design ◽  
Closed System ◽  
Error Control ◽  
Viterbi Algorithm ◽  
Quantum Systems ◽  
Decoding Algorithm ◽  
Error Control Coding ◽  
Unitary Evolution ◽  
System Quantum

Novel convolution-based multiple-stream error-control coding and decoding methods and their corresponding circuits are introduced. The new coding method applies the reversibility property in (1) the convolution-based encoder for multiple-stream error-control encoding and (2) in the new reversible Viterbi decoding algorithm for multiple-stream error-correction decoding. The complete synthesis of quantum circuits for the quantum realization of the new quantum Viterbi cell in the quantum domain (Q-domain) is also introduced, and the associated quantum computing representations and operations are presented. In quantum mechanics, a closed system is an isolated system that cannot exchange energy or matter with its surroundings and does not interact with other quantum systems. Closed quantum systems obey the unitary evolution and thus they are reversible. Reversibility property in error-control coding can be important for the following main reasons: (1) reversibility is a basic requirement for low-power circuit design in future technologies such as in closed-system quantum computing (QC), (2) reversibility leads to super-speedy encoding/decoding operations because of the superposition and entanglement properties that exist in the reversible closed-system quantum computing circuits and systems, and (3) the reversibility relationship between multiple-streams of data can be used for the correction of errors that are usually uncorrectable using the implemented decoding algorithm such as in the case of triple-errors that are uncorrectable using the irreversible Viterbi algorithm.

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