scholarly journals Adaptive Quantum Computation, Constant Depth Quantum Circuits and Arthur-Merlin Games

2004 ◽  
Vol 4 (2) ◽  
pp. 134-145 ◽  
Author(s):  
B.M. Terhal ◽  
D.P. DiVincenzo
Keyword(s):  
Quantum Computation ◽  
High Accuracy ◽  
Quantum Circuits ◽  
Constant Depth ◽  
Present Evidence ◽  
Quantum Computations

We present evidence that there exist quantum computations that can be carried out in constant depth, using 2-qubit gates, that cannot be simulated classically with high accuracy. We prove that if one can simulate these circuits classically efficiently then ${\rm BQP} \subseteq {\rm AM}$.

Commuting quantum circuits: efficiently classical simulations versus hardness results

2013 ◽  
Vol 13 (1&2) ◽  
pp. 54-72
Author(s):  
Xiaotong Ni ◽  
Maarten van den Nest
Keyword(s):  
Sampling Methods ◽  
Quantum Effects ◽  
High Accuracy ◽  
Quantum Circuits ◽  
Computational Power ◽  
Restricted Class ◽  
Constant Depth ◽  
Single Qubit ◽  
Single Qudit ◽  
Local Circuits

The study of quantum circuits composed of commuting gates is particularly useful to understand the delicate boundary between quantum and classical computation. Indeed, while being a restricted class, commuting circuits exhibit genuine quantum effects such as entanglement. In this paper we show that the computational power of commuting circuits exhibits a surprisingly rich structure. First we show that every 2-local commuting circuit acting on $d$-level systems and followed by single-qudit measurements can be efficiently simulated classically with high accuracy. In contrast, we prove that such strong simulations are hard for 3-local circuits. Using sampling methods we further show that all commuting circuits composed of exponentiated Pauli operators $e^{i\theta P}$ can be simulated efficiently classically when followed by single-qubit measurements. Finally, we show that commuting circuits can efficiently simulate certain non-commutative processes, related in particular to constant-depth quantum circuits. This gives evidence that the power of commuting circuits goes beyond classical computation.

scholarly journals Connectivity matrix model of quantum circuits and its application to distributed quantum circuit optimization

2021 ◽  
Vol 20 (7) ◽  
Author(s):  
Ismail Ghodsollahee ◽  
Zohreh Davarzani ◽  
Mariam Zomorodi ◽  
Paweł Pławiak ◽  
Monireh Houshmand ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Quantum Circuit ◽  
Quantum Circuits ◽  
Connectivity Matrix ◽  
Circuit Optimization ◽  
Novel Approach ◽  
The Matrix ◽  
Minimum Number ◽  
Two Phases

AbstractAs quantum computation grows, the number of qubits involved in a given quantum computer increases. But due to the physical limitations in the number of qubits of a single quantum device, the computation should be performed in a distributed system. In this paper, a new model of quantum computation based on the matrix representation of quantum circuits is proposed. Then, using this model, we propose a novel approach for reducing the number of teleportations in a distributed quantum circuit. The proposed method consists of two phases: the pre-processing phase and the optimization phase. In the pre-processing phase, it considers the bi-partitioning of quantum circuits by Non-Dominated Sorting Genetic Algorithm (NSGA-III) to minimize the number of global gates and to distribute the quantum circuit into two balanced parts with equal number of qubits and minimum number of global gates. In the optimization phase, two heuristics named Heuristic I and Heuristic II are proposed to optimize the number of teleportations according to the partitioning obtained from the pre-processing phase. Finally, the proposed approach is evaluated on many benchmark quantum circuits. The results of these evaluations show an average of 22.16% improvement in the teleportation cost of the proposed approach compared to the existing works in the literature.

scholarly journals Quantum Circuits for Dynamic Runtime Assertions in Quantum Computation

2019 ◽  
Author(s):  
Ji Liu ◽  
Greg Byrd ◽  
Huiyang Zhou
Keyword(s):  
Open Source ◽  
Quantum Computation ◽  
Quantum Computer ◽  
Quantum Circuits ◽  
Intermediate Scale

In this paper, we propose quantum circuits to enable dynamic assertions for classical values, entanglement, and superposition. This enables a dynamic debugging primitive, driven by a programmer’s understanding of the correct behavior of the quantum program. We show that besides generating assertion errors, the assertion logic may also force the qubits under test to be into the desired state. Besides debugging, our proposed assertion logic can also be used in noisy intermediate scale quantum (NISQ) systems to filter out erroneous results, as demonstrated on a 20-qubit IBM Q quantum computer. Our proposed assertion circuits have been implemented as functions in the open-source Qiskit tool.

scholarly journals Improved Resource State for Verifiable Blind Quantum Computation

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 996
Author(s):  
Qingshan Xu ◽  
Xiaoqing Tan ◽  
Rui Huang
Keyword(s):  
Quantum Computing ◽  
Quantum Computation ◽  
Fault Tolerant ◽  
Maximal Degree ◽  
Recent Advances ◽  
Quantum Computations ◽  
Blind Quantum Computation ◽  
Computation Graph ◽  
Resource State

Recent advances in theoretical and experimental quantum computing raise the problem of verifying the outcome of these quantum computations. The recent verification protocols using blind quantum computing are fruitful for addressing this problem. Unfortunately, all known schemes have relatively high overhead. Here we present a novel construction for the resource state of verifiable blind quantum computation. This approach achieves a better verifiability of 0.866 in the case of classical output. In addition, the number of required qubits is 2N+4cN, where N and c are the number of vertices and the maximal degree in the original computation graph, respectively. In other words, our overhead is less linear in the size of the computational scale. Finally, we utilize the method of repetition and fault-tolerant code to optimise the verifiability.

scholarly journals Universal logical gates with constant overhead: instantaneous Dehn twists for hyperbolic quantum codes

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 180 ◽  
Author(s):  
Ali Lavasani ◽  
Guanyu Zhu ◽  
Maissam Barkeshli
Keyword(s):  
Quantum Computation ◽  
Fault Tolerant ◽  
Hyperbolic Surface ◽  
Constant Factor ◽  
Basic Question ◽  
Quantum Codes ◽  
Constant Depth ◽  
Dehn Twists ◽  
Local Operators ◽  
Time Overhead

A basic question in the theory of fault-tolerant quantum computation is to understand the fundamental resource costs for performing a universal logical set of gates on encoded qubits to arbitrary accuracy. Here we consider qubits encoded with constant space overhead (i.e. finite encoding rate) in the limit of arbitrarily large code distance d through the use of topological codes associated to triangulations of hyperbolic surfaces. We introduce explicit protocols to demonstrate how Dehn twists of the hyperbolic surface can be implemented on the code through constant depth unitary circuits, without increasing the space overhead. The circuit for a given Dehn twist consists of a permutation of physical qubits, followed by a constant depth local unitary circuit, where locality here is defined with respect to a hyperbolic metric that defines the code. Applying our results to the hyperbolic Fibonacci Turaev-Viro code implies the possibility of applying universal logical gate sets on encoded qubits through constant depth unitary circuits and with constant space overhead. Our circuits are inherently protected from errors as they map local operators to local operators while changing the size of their support by at most a constant factor; in the presence of noisy syndrome measurements, our results suggest the possibility of universal fault tolerant quantum computation with constant space overhead and time overhead of O(d/log⁡d). For quantum circuits that allow parallel gate operations, this yields the optimal scaling of space-time overhead known to date.

scholarly journals Models of quantum computation and quantum programming languages

2011 ◽  
Vol 59 (3) ◽  
pp. 305-324 ◽  
Author(s):  
J. Miszczak
Keyword(s):  
Information Theory ◽  
Programming Languages ◽  
Quantum Computation ◽  
Computational Models ◽  
Random Access ◽  
Quantum Information Theory ◽  
Quantum Circuits ◽  
Quantum Programming Languages ◽  
Quantum Programming ◽  
Quantum Turing Machine

Models of quantum computation and quantum programming languagesThe goal of the presented paper is to provide an introduction to the basic computational models used in quantum information theory. We review various models of quantum Turing machine, quantum circuits and quantum random access machine (QRAM) along with their classical counterparts. We also provide an introduction to quantum programming languages, which are developed using the QRAM model. We review the syntax of several existing quantum programming languages and discuss their features and limitations.

scholarly journals A general protocol for distributed quantum gates

2021 ◽  
Vol 20 (8) ◽  
Author(s):  
Moein Sarvaghad-Moghaddam ◽  
Mariam Zomorodi
Keyword(s):  
Quantum Computation ◽  
Quantum Circuits ◽  
Quantum Gates ◽  
Toffoli Gate

AbstractIn distributed quantum computation, quantum remote-controlled gates are used frequently and applied on separate nodes or subsystems of a network. One of the universal and well-known controlled gates is the n-qubit controlled-NOT gate, especially Toffoli gate for the case of three qubits, which are frequently used to synthesize quantum circuits. In this paper, we considered a more general case, an n-qubit controlled-U gate, and present a general protocol for implementing these gates remotely with minimum required resources. Then, the proposed method is applied to implement a Toffoli gate in bipartite and tripartite systems. In this method, we considered cases in which a group of qubits belongs to one subsystem of the network. Then, we improved its consumption resources.

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