scholarly journals Single qubit neural quantum circuit for solving Exclusive-OR

MethodsX ◽  
2021 ◽  
pp. 101573
Author(s):  
I.V. Grossu
Keyword(s):  
Quantum Circuit ◽  
Single Qubit ◽  
Exclusive Or

An upper bound on the threshold quantum decoherence rate

2004 ◽  
Vol 4 (3) ◽  
pp. 222-228
Author(s):  
A.A. Razborov
Keyword(s):  
Upper Bound ◽  
Random Noise ◽  
Quantum Circuit ◽  
Quantum Decoherence ◽  
Single Qubit ◽  
Constant Rate ◽  
Decoherence Rate

Let $\eta_0$ be the supremum of those $\eta$ for which every poly-size quantum circuit can be simulated by another poly-size quantum circuit with gates of fan-in $\leq 2$ that tolerates random noise independently occurring on all wires at the constant rate $\eta$. Recent fundamental results showing the principal fact $\eta_0>0$ give estimates like $\eta_0\geq 10^{-6}\mbox{--}10^{-4}$, whereas the only upper bound known before is $\eta_0\leq 0.74$.}{In this note we improve the latter bound to $\eta_0\leq 1/2$, under the assumption ${\bf QP}\not\subseteq {\bf QNC^1}$. More generally, we show that if the decoherence rate $\eta$ is greater than 1/2, then we can not even store a single qubit for more than logarithmic time. Our bound also generalizes to the simulating circuits allowing gates of any (constant) fan-in $k$, in which case we have $\eta_0\leq 1-\frac 1k$.

scholarly journals Measuring the Tangle of Three-Qubit States

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 436 ◽  
Author(s):  
Adrián Pérez-Salinas ◽  
Diego García-Martín ◽  
Carlos Bravo-Prieto ◽  
José Latorre
Keyword(s):  
Direct Measurement ◽  
Canonical Form ◽  
Quantum Circuit ◽  
Quantum Gates ◽  
Tripartite Entanglement ◽  
Single Qubit ◽  
Optimal Values ◽  
Random States ◽  
Qubit States ◽  
Computational Basis

We present a quantum circuit that transforms an unknown three-qubit state into its canonical form, up to relative phases, given many copies of the original state. The circuit is made of three single-qubit parametrized quantum gates, and the optimal values for the parameters are learned in a variational fashion. Once this transformation is achieved, direct measurement of outcome probabilities in the computational basis provides an estimate of the tangle, which quantifies genuine tripartite entanglement. We perform simulations on a set of random states under different noise conditions to asses the validity of the method.

Experimental demonstration of optimized quantum process tomography on the IBM quantum experience

2020 ◽  
pp. 2040004
Author(s):  
Akshay Gaikwad ◽  
Krishna Shende ◽  
Kavita Dorai
Keyword(s):  
Quantum Circuit ◽  
Quantum Gates ◽  
Experimental Demonstration ◽  
Superconducting Qubit ◽  
Quantum Process ◽  
Single Qubit ◽  
Quantum Process Tomography ◽  
Process Tomography ◽  
Quantum Processor ◽  
Least Squares Optimization

We experimentally performed complete and optimized quantum process tomography of quantum gates implemented on superconducting qubit-based IBM QX2 quantum processor via two constrained convex optimization (CCO) techniques: least squares optimization and compressed sensing optimization. We studied the performance of these methods by comparing the experimental complexity involved and the experimental fidelities obtained. We experimentally characterized several two-qubit quantum gates: identity gate, a controlled-NOT gate, and a SWAP gate. The general quantum circuit is efficient in the sense that the data needed to perform CCO-based process tomography can be directly acquired by measuring only a single qubit. The quantum circuit can be extended to higher dimensions and is also valid for other experimental platforms.

scholarly journals ON THE POWER QUANTUM COMPUTATION OVER REAL HILBERT SPACES

2013 ◽  
Vol 11 (01) ◽  
pp. 1350001 ◽  
Author(s):  
MATTHEW McKAGUE
Keyword(s):  
Hilbert Space ◽  
Quantum Computation ◽  
Hilbert Spaces ◽  
Quantum Circuit ◽  
Complex Hilbert Space ◽  
Complexity Classes ◽  
Complex Numbers ◽  
Real Numbers ◽  
Single Qubit ◽  
Quantum Complexity

We consider the power of various quantum complexity classes with the restriction that states and operators are defined over a real, rather than complex, Hilbert space. It is well known that a quantum circuit over the complex numbers can be transformed into a quantum circuit over the real numbers with the addition of a single qubit. This implies that BQP retains its power when restricted to using states and operations over the reals. We show that the same is true for QMA (k), QIP (k), QMIP and QSZK.

scholarly journals Modelling of Grover’s quantum search algorithms: implementations of Simple quantum simulators on classical computers

2020 ◽  
pp. 65-128
Author(s):  
Sergey Ulyanov ◽  
Andrey Reshetnikov ◽  
Olga Tyatyushkina
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Search Algorithm ◽  
Quantum Circuit ◽  
Unitary Matrix ◽  
Single Qubit ◽  
Simple Quantum ◽  
Grover’S Search Algorithm ◽  
The Cost ◽  
Universal Gate

Models of Grover’s search algorithm is reviewed to build the foundation for the other algorithms. Thereafter, some preliminary modifications of the original algorithms by others are stated, that increases the applicability of the search procedure. A general quantum computation on an isolated system can be represented by a unitary matrix. In order to execute such a computation on a quantum computer, it is common to decompose the unitary into a quantum circuit, i.e., a sequence of quantum gates that can be physically implemented on a given architecture. There are different universal gate sets for quantum computation. Here we choose the universal gate set consisting of CNOT and single-qubit gates. We measure the cost of a circuit by the number of CNOT gates as they are usually more difficult to implement than single qubit gates and since the number of single-qubit gates is bounded by about twice the number of CNOT’s.

scholarly journals Data re-uploading for a universal quantum classifier

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 226 ◽  
Author(s):  
Adrián Pérez-Salinas ◽  
Alba Cervera-Lierta ◽  
Elies Gil-Fuster ◽  
José I. Latorre
Keyword(s):  
Quantum Circuit ◽  
Complex Data ◽  
Bloch Sphere ◽  
Single Qubit ◽  
Multiple Dimensions ◽  
Universal Quantum

A single qubit provides sufficient computational capabilities to construct a universal quantum classifier when assisted with a classical subroutine. This fact may be surprising since a single qubit only offers a simple superposition of two states and single-qubit gates only make a rotation in the Bloch sphere. The key ingredient to circumvent these limitations is to allow for multiple data re-uploading. A quantum circuit can then be organized as a series of data re-uploading and single-qubit processing units. Furthermore, both data re-uploading and measurements can accommodate multiple dimensions in the input and several categories in the output, to conform to a universal quantum classifier. The extension of this idea to several qubits enhances the efficiency of the strategy as entanglement expands the superpositions carried along with the classification. Extensive benchmarking on different examples of the single- and multi-qubit quantum classifier validates its ability to describe and classify complex data.

Both Toffoli and Controlled-NOT need little help to universal quantum computing

2003 ◽  
Vol 3 (1) ◽  
pp. 84-92
Author(s):  
Y-Y Shi
Keyword(s):  
Quantum Computing ◽  
Quantum Computation ◽  
Quantum Circuit ◽  
Single Qubit ◽  
Universal Quantum ◽  
Qubit Gate ◽  
Computational Basis ◽  
Universal Gates

What additional gates are needed for a set of classical universal gates to do universal quantum computation? We prove that any single-qubit real gate suffices, except those that preserve the computational basis. The Gottesman-Knill Theorem implies that any quantum circuit involving only the Controlled-NOT and Hadamard gates can be efficiently simulated by a classical circuit. In contrast, we prove that Controlled-NOT plus any single-qubit real gate that does not preserve the computational basis and is not Hadamard (or its like) are universal for quantum computing. Previously only a generic gate, namely a rotation by an angle incommensurate with \pi, is known to be sufficient in both problems, if only one single-qubit gate is added.

Quantum lower bounds for fanout

2006 ◽  
Vol 6 (1) ◽  
pp. 46-57
Author(s):  
M. Fang ◽  
S. Fenner ◽  
F. Green ◽  
S. Homer ◽  
Y. Zhang
Keyword(s):  
Lower Bounds ◽  
Quantum Circuit ◽  
Circuit Theory ◽  
Quantum Circuits ◽  
Constant Number ◽  
Constant Depth ◽  
Arbitrary Size ◽  
Single Qubit ◽  
Toffoli Gates ◽  
Circuit Family

We consider the resource bounded quantum circuit model with circuits restricted by the number of qubits they act upon and by their depth. Focusing on natural universal sets of gates which are familiar from classical circuit theory, several new lower bounds for constant depth quantum circuits are proved. The main result is that parity (and hence fanout) requires log depth quantum circuits, when the circuits are composed of single qubit and arbitrary size Toffoli gates, and when they use only constantly many ancill\ae. Under this constraint, this bound is close to optimal. In the case of a non-constant number $a$ of ancill\ae\ and $n$ input qubits, we give a tradeoff between $a$ and the required depth, that results in a non-constant lower bound for fanout when $a = n^{1-o(1)}$. We also show that, regardless of the number of ancill\ae\, arbitrary arity Toffoli gates cannot be simulated exactly by a constant depth circuit family with gates of bounded arity.

Hardness of classically simulating quantum circuits with unbounded Toffoli and fan-out gates

2014 ◽  
Vol 14 (13&14) ◽  
pp. 1149-1164
Author(s):  
Yasuhiro Takahashi ◽  
Takeshi Yamazaki ◽  
Kazuyuki Tanaka
Keyword(s):  
Probability Distribution ◽  
Quantum Circuit ◽  
Quantum Circuits ◽  
Constant Depth ◽  
Toffoli Gate ◽  
Single Qubit ◽  
Polynomial Size ◽  
Toffoli Gates ◽  
Output Probability ◽  
Universal Gates

We study the classical simulatability of constant-depth polynomial-size quantum circuits followed by only one single-qubit measurement, where the circuits consist of universal gates on at most two qubits and additional gates on an unbounded number of qubits. First, we consider unbounded Toffoli gates as additional gates and deal with the weak simulation, i.e., sampling the output probability distribution. We show that there exists a constant-depth quantum circuit with only one unbounded Toffoli gate that is not weakly simulatable, unless $\bqp \subseteq \postbpp \cap \am$. Then, we consider unbounded fan-out gates as additional gates and deal with the strong simulation, i.e., computing the output probability. We show that there exists a constant-depth quantum circuit with only two unbounded fan-out gates that is not strongly simulatable, unless $\p = \pp$. These results are in contrast to the fact that any constant-depth quantum circuit without additional gates on an unbounded number of qubits is strongly and weakly simulatable.

Algorithm for generating optimal tests for exclusive-or networks

1991 ◽  
Vol 138 (2) ◽  
pp. 93 ◽  
Author(s):  
W.H. Debany ◽  
C.R.P. Hartmann ◽  
T.J. Snethen
Keyword(s):  
Optimal Tests ◽  
Exclusive Or
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