Computational Circuits

Sohrab Sajadimanesh, Ehsan Atoofian

Contemporary quantum computers with tens to hundreds of physical quantum bits (qubits) are susceptible to quantum noise. As a result, running quantum circuits on these computers is error prone. In particular, deep quantum circuits with a large number of quantum gates and qubits are more likely to fail on quantum computers. In this work, we propose a design for the quantum arithmetic division operation which runs successfully on contemporary quantum computers. A quantum division circuit is needed for realization of quantum algorithms in scientific and image processing applications. While there have been a limited number of prior works on quantum division, none of them can be implemented on quantum computers due to excessive circuit complexity. We propose a different design that exploits dynamic circuits and approximate computing to deploy a quantum division circuit in quantum computers. The dynamic circuit is a new feature in recent quantum computers for midcircuit measurement in hardware. We exploit this feature to reduce the number of qubits and increase the fidelity of quantum division. We also exploit approximate computing to overcome noise in quantum hardware. We carefully tune the scope of approximation in our circuits to offer an acceptable level of accuracy. We run our division circuit on an IBM quantum computer and show that our circuit overcomes quantum noise and generates meaningful results.

Bernard Zygelman

Bernard Zygelman

Himanshu Thapliyal, Edgard Muñoz‐Coreas

Quantum computing is an emerging method of computation that promises to accomplish computational tasks and algorithms that are too difficult to perform on existing computing paradigms. Some of the promising applications of quantum computing includes number theory, encryption, search, and scientific computation. Circuits must be designed to apply quantum machines to these applications. This work introduces quantum circuit design. We provide a brief introduction to quantum computing, and then, we illustrate gates used in quantum circuit design. We conclude by introducing quantum circuits for arithmetic operations.

Colin P. Williams

Alexis De Vos, Stijn De Baerdemacker

Whereas quantum computing circuits follow the symmetries of the unitary Lie group, classical reversible computation circuits follow the symmetries of a finite group, i.e., the symmetric group. We confront the decomposition of an arbitrary classical reversible circuit with w bits and the decomposition of an arbitrary quantum circuit with w qubits. Both decompositions use the control gate as building block, i.e., a circuit transforming only one (qu)bit, the transformation being controlled by the other w−1 (qu)bits. We explain why the former circuit can be decomposed into 2w − 1 control gates, whereas the latter circuit needs 2w − 1 control gates. We investigate whether computer circuits, not based on the full unitary group but instead on a subgroup of the unitary group, may be decomposable either into 2w − 1 or into 2w − 1 control gates.