From quantum effects to quantum circuits - Toward the quantum computer

María Luisa Dalla Chiara, Roberto Giuntini, Roberto Leporini +1 more

Yusuke Hama, Hirofumi Nishi

Near-term quantum computers have been built as intermediate-scale quantum devices and are fragile against quantum noise effects, namely, NISQ devices. Traditional quantum-error-correcting codes are not implemented on such devices and to perform quantum computation in good accuracy with these machines we need to develop alternative approaches for mitigating quantum computational errors. In this work, we propose quantum error mitigation (QEM) scheme for quantum computational errors which occur due to couplings with environments during gate operations, i.e., decoherence. To establish our QEM scheme, first we estimate the quantum noise effects on single-qubit states and represent them as groups of quantum circuits, namely, quantum-noise-effect circuit groups. Then our QEM scheme is conducted by subtracting expectation values generated by the quantum-noise-effect circuit groups from those obtained by the quantum circuits for the quantum algorithms under consideration. As a result, the quantum noise effects are reduced, and we obtain approximately the ideal expectation values via the quantum-noise-effect circuit groups and the numbers of elementary quantum circuits composing them scale polynomial with respect to the products of the depths of quantum algorithms and the numbers of register bits. To numerically demonstrate the validity of our QEM scheme, we run noisy quantum simulations of qubits under amplitude damping effects for four types of quantum algorithms. Furthermore, we implement our QEM scheme on IBM Q Experience processors and examine its efficacy. Consequently, the validity of our scheme is verified via both the quantum simulations and the quantum computations on the real quantum devices. Our QEM scheme is solely composed of quantum-computational operations (quantum gates and measurements), and thus, it can be conducted by any type of quantum device. In addition, it can be applied to error mitigation for many other types of quantum noise effects as well as noisy quantum computing of long-depth quantum algorithms.

Yuntao Liu, Jayden John, Qian Wang

In recent years, quantum computing has started to demonstrate superior efficiency to classical computing. In quantum computing, quantum circuits that implement specific quantum algorithms are usually not directly executable on quantum computer hardware. Quantum circuit compilers decompose high-level quantum gates into the hardware's native gates and optimize the circuits for accuracy and performance. However, untrusted quantum compilers risk stealing original quantum designs (quantum circuits), leading to the theft of sensitive intellectual property (IP). In classical computing, logic locking is a family of techniques to secure integrated circuit (ICs) designs against reverse engineering and IP piracy. This technique involves inserting a keyed value into the circuit, ensuring the correct output is achieved only with the correct key. To address similar issues in quantum circuit protection, we propose an enhanced locking technique for quantum circuits (E-LoQ) where multiple key bits can be condensed into one key qubit. Compared to previous work that used one qubit for each key bit, our approach achieves higher security levels. We have demonstrated the practicality of our method through experiments on a set of benchmark quantum circuits. The effectiveness of E-LoQ was measured by assessing the divergence distance from the original circuit. Our results demonstrate that E-LoQ effectively conceals the function of the original quantum circuit, with an average fidelity degradation of less than 1 %.

Daniele Cuomo

Shakhawan Salih Abdullah

A correct simulation of a quantum circuit on a classical computer is more important because of their future use.The main purpose of this work is to illustrate a full adder circuit by using a standard Mathematica add-on package.The circuit can be constructed by using CNOT-based quantum gates.The program provides a curriculum unit, to generate the basic elements that make up quantum circuit.This paper shows effective computational design by using analogy of classical circuits.We presented an explicit example to show efficiency of the 4 qubit full adder circuit on classical computer.The method given in this paper can be used to design various quantum circuits.

François Chapeau‐Blondeau