Physics of computation and the quantum computing challenge

Man Hong Yung

This is a study of several physical challenges for building a quantum computer, a hypothetical device which is capable of accomplishing tasks unachievable by the classical model of computation. In chapter 1, we will give an overview of quantum computation and discuss the physical challenges for building a realistic quantum computer. In chapter 2, we shall explore the applications of quantum computation for the simulation of molecular quantum systems. In particular, an efficient algorithm for evaluating the partition function (and hence free energy) is proposed. In chapter 3, quantum information transfer over spin chains is then discussed. A proof about the most efficient way to transfer quantum information in one dimension is constructed. In chapter 4, we shall consider the effects of quantum correlation induced by quantum mechanical environments on the efficiency of the methods of quantum error correction. In chapter 5, we consider how the thermal noise affects the reliability of an adiabatic quantum computer.

G. Falci, Elisabette Paladino

Umesh V. Vazirani

S. B. Goyal, Anand Singh Rajawat, Ruchi Mittal +1 more

The convergence of traditional cyber-physical systems (CPS), quantum computing, and artificial intelligence (AI) gives rise to a novel system known as a quantum cyber-physical system (QCPS). This study aims to examine the integration of post-quantum models enabled by AI into quantum computing platforms and systems (QCPS). The merging of AI methodologies and the computational capabilities of quantum computers presents a novel approach to addressing intricate challenges in CPS. This context has several potential outcomes, including enhanced safety measures, improved resource allocation, and increased efficiency in quantum operations. Nevertheless, it is imperative to meticulously examine several challenges that arise in this context, including quantum decoherence, the interpretability of AI models, and the nascent stage of post-quantum algorithms. Overcoming these challenges will facilitate the advent of a novel era characterized by the integration of quantum-enabled systems, hence holding the capacity to revolutionize numerous domains within the economy and societal structure.

H. Thomas

Bodhisatwa Sadhu, Kevin Tien, Sudipto Chakraborty +26 more

Quantum computers offer the promise of accelerated solutions for types of problems that are computationally unaffordable or intractable for classical computers, such as the simulation of quantum mechanics itself, quantum chemistry, and mathematical challenges like factoring large numbers. However, the relatively high error rate per quantum computing operation in the systems of today and of those expected to be developed in the future remains a key obstacle. To address this challenge, quantum error correction (QEC), which enables the creation of error-corrected (logical) qubits from a collection of physical qubits, is required. Depending on the choice of QEC code, hundreds of physical qubits may be required to implement a single logical qubit. As a result, the race to the creation of quantum computing systems capable of outperforming classical computing systems is largely a race to create quantum computers at the scale needed to support QEC. The criticality of scaling is evident in the quantum computing roadmaps produced by major research labs in this field, such as the one from IBM shown in Fig. 1. Starting from systems with only a few physical qubits a few years ago, the roadmap projects quantum computers with around 100,000 physical qubits and thousands of logical qubits by 2033 or so.