### Quantum-computing related developments

On this page we post about interesting quantum-computing related research and news which we are following.

On this page we post about interesting quantum-computing related research and news which we are following.

November 15, 2018

- Source: The Boston Consulting Group

This report by The Boston Consulting Group, a strategy consulting firm, targets business executives and other people looking for a broader market overview on quantum computing. The authors (Philipp Gerbert et al.) provide some insight in where the technology currently stands, who is who in the emerging ecosystem, and the potentially interesting applications. The report also analyzes some of the leading indicators of investments, patents, and publications, which countries and entities are most active and the status and prospects for the main categories of quantum hardware technologies. Additionally, the report aims to provide a simple framework for understanding quantum algorithms and assessing their applicability and potential. Finally, the authors provide their view of what can be expected in the next five to ten years, and what corporates should be doing, or getting ready for, in response.

August 27, 2018

- Source: ArXiv

Ever since the publication of Shor’s algorithm in 1994, efficient integer factorization has been a key application area envisioned for quantum-computers, with important implications for the security of some of the most used cryptosystems. Because Shor’s algorithm requires a large-scale fault-tolerant quantum-processor, RSA-3072 encryption was so-far believed to remain safe until 2030. However, in recent years hybrid (classical-quantum) alternatives have been developed for many important quantum-algorithms. Such hybrid algorithms can be run on current-day noisy and small-scale quantum-processors. In this paper Eric Anschuetz et al. describe such a hybrid alternative for Shor’s algorithm, which they call variational quantum factoring (VQF). If some pre-processing is applied VQF scales with O(n), n being the number of bits of the integer being factored. If VQF can be optimized to scale well up to 3000+ qubits, which is very challenging, but not completely unthinkable, and if we assume the number of physical qubits in quantum-processors doubles every year, quantum-processors could have sufficiently high qubit count to break RSA-3072 as early as 2025. However, as VQF relies on a quantum-optimization algorithm (QAOA) it seems unlikely that the speed-up of VQF could be more than quadratic, which means that the runtime for breaking RSA-3072 could very well be prohibitively long and that doubling the RSA-6144 (double the key-length) would again be just as safe as RSA-3072 is currently.

July 11, 2018

- Source: Arxiv

Many financial services players are experimenting with quantum-computing so that they can be the first to start exploiting its benefits in speed-up and tractability. Algorithms have been developed for a wide range of finance related topics e.g. Monte Carlo simulation, portfolio optimization, anomaly (fraud) detection, market forecasting and reduction of slippage. In this paper Orus et al. provide a nice overview of most of these applications. Although the paper puts much emphasis on what has been done with quantum-annealers, applying the Quantum Approximate Optimization Algorithm (QAOA) lets us map all of them to universal-gate devices, which ensures that these applications stay relevant even when annealers become obsolete.

May 16, 2018

- Source: The Boston Consulting Group

This report by The Boston Consulting Group, a strategy consulting firm, provides both an introductory status overview of current and near-term qubit technologies and of practical quantum-computing applications as well as a longer-term outlook of the quantum-computing market, which the authors (Massimo Russo et al.) estimate could be as large as $50bln by 2030. The report also provides some advice to corporates on how to prepare for the arrival of practical quantum-computing applications

April 19, 2018

- Source: Arxiv

Recently, promising experimental results have been shown for quantum-chemistry calculations using small, noisy quantum processors. As full scale fault-tolerant error correction is still many years away, near-term quantum computers will have a limited number of qubits, and each qubit will be noisy. Methods that reduce noise and correct errors without doing full error correction on every qubit will help extend the range of interesting problems that can be solved in the near-term. In this paper Otten et al. present a scheme for accounting (and removal) of errors in observables determined from quantum algorithms and apply this scheme to the variational quantum eigensolver algorithm, simulating the calculation of the ground state energy of equilibrium H2 and LiH in the presence of several noise sources, including amplitude damping, dephasing, thermal noise, and correlated noise. They show that their scheme provides a decrease in the needed quality of the qubits by up to two orders of magnitude.

April 15, 2018

- Source: Arxiv

In this paper Bian et al. compare four different quantum simulation methods to simulate the ground state energy of the Hamiltonian for the water molecule on a quantum computer, being 1) the phase estimation algorithm based on Trotter decomposition, 2) phase estimation based on the direct implementation of the Hamiltonian, 3) direct measurement based on the implementation of the Hamiltonian and 4) the variational quantum eigensolver (classical-quantum hybrid) algorithm. They compare a.o. the required number of qubits, gate-complexity, accuracy/error.

April 10, 2018

- Source: ArXiv

In this paper, Patrick J. Coles et al., aim to explain the principles of quantum programming straight-forward algebra that makes understanding the underlying quantum mechanics optional (but still fascinating). The authors give an introduction to quantum computing algorithms and their implementation on real quantum hardware and survey 20 different quantum algorithms, attempting to describe each in a succinct and self-contained fashion. They show how these algorithms can be implemented on an actual quantum-processor (in this case an IBM QPU) and in each case discuss the results of the implementation with respect to differences of the results on a simulator (QVM) or the actual processor (QPU).

March 27, 2018

- Source: Arxiv

Efficient quantum simulations of classically intractable instances of the associated electronic structure problem promise breakthroughs in our understanding of basic chemistry and could revolutionize research into new materials, pharmaceuticals, and industrial catalysts. In Quantum Computational Chemistry solutions, the Variational Quantum Eigensolver (VQE) algorithm offers a hybrid classical-quantum, and thus low quantum circuit depth, alternative to the Phase Estimation algorithm used to measure the ground-state energy of a molecular Hamiltonian. In this paper, Hempel et al. use a digital quantum simulator based on trapped ions to experimentally investigate the VQE algorithm for the calculation of molecular ground state energies of two simple molecules (H2 and LiH) and experimentally demonstrate and compare different encoding methods using up to four qubits.

March 7, 2018

- Source: Arxiv

In this paper Flamini et al. provide a comprehensive overview of the current (March 2018) state of the art in the field of photonic quantum information processing including quantum communication and photonic quantum simulation.

March 7, 2018

- Source: Arxiv

Clustering is a form of unsupervised machine learning, where instances are organized into groups whose members share similarities. The assignments are, in contrast to classification, not known a priori, but generated by the algorithm. In this paper, Neukart et al. present an algorithm for quantum-assisted cluster analysis (QACA) that makes use of the topological properties of a D-Wave 2000Q quantum processing unit (QPU). They explain how the problem can be expressed as a quadratic unconstrained binary optimization (QUBO) problem, and show that the introduced quantum-assisted clustering algorithm is, regarding accuracy, equivalent to commonly used classical clustering algorithms.

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