Quantum Computers as Universal Quantum Simulators: State‐of‐the‐Art and Perspectives

Abstract

The past few years have witnessed the concrete and fast spreading of quantum technologies for practical computation and simulation. In particular, quantum computing platforms based on either trapped ions or superconducting qubits have become available for simulations and benchmarking, with up to few tens of qubits that can be reliably initialized, controlled, and measured. The present Review aims at giving a comprehensive outlook on the state‐of‐the‐art capabilities offered from these near‐term noisy devices as universal quantum simulators, that is, programmable quantum computers potentially able to calculate the time evolution of many physical models. First, a pedagogic overview on the basic theoretical background pertaining digital quantum simulations is given, with a focus on hardware‐dependent mapping of spin‐type Hamiltonians into the corresponding quantum circuit as a key initial step toward simulating more complex models. Then, the main experimental achievements obtained in the last decade are reviewed, focusing on the digital quantum simulation of such spin models by employing two leading quantum architectures. Their performances are compared, and future challenges are outlined, also in view of prospective hybrid technologies, towards the ultimate goal of reaching the long‐sought quantum advantage for the simulation of complex many‐body models in the physical sciences.

Dissipative generation of pure steady states and a gambler's ruin problem

“…Deep understanding of the quantum part of the criterion remains a challenge for the future. From the applicative viewpoint, our criterion allows dissipative targeting of pure states or simple mixtures of few quantum states, a task of fundamental importance in the initialization of quantum simulators [32] (see also [33] for an up-to-date review of recent and ongoing experiments).…”

Quantifying the Sensitivity to Errors in Analog Quantum Simulation

“…Assuming that |ψ 0 can be prepared with high accuracy, then errors will arise in the simulator because of an imperfect implementation of H . The nature of such imperfections can be of various kinds, and they depend on the particular physical platform [30].…”

Quantum Computing: An Entanglement Measurement

“…For effective realization and understanding of quantum property of entanglement and other quantum primitives of quantum teleportation, superposition of states, quantum walk among many others various quantum simulators and emulators have been developed [38,39,40,41]. However, limitations of realization are more pertinent as the same are observed over of special purpose simulators and emulators over a classical computers [42,43,44,45,46,47,48,49,50]. Realization of entanglement by means of open source software projects like IBM Q experience though gives an approximate idea for preliminary study and validation of any developed concept or application at the computational level, however, it does provide an actual physical outlook into the difficulties that might be witnessed while implementing the concept practically for use.…”