A 2048 qubit D-Wave 2000Q™ quantum computer was used to predict phase transitions within a particular quantum mechanical system known as the transverse field Ising model. This work has significantly raised the bar in regards to size and complexity of the problems addressed by fully programmable quantum computers. The D-Wave system is capable of programming the individual interactions between spins, whereas prior work with other quantum devices was limited to studying systems in which those interactions could not be individually programmed.
Researchers used a 2048-qubit D-Wave quantum computer to study the transverse field Ising model on 3-dimensional simple cubic lattices up to dimensions of 8x8x8 (512 quantum spins). The magnetic phases, and more importantly the phase transitions, were correctly identified within the 3-dimensional space as a function of quantum mechanical energy scale, the strength of interactions between spins, and disorder among the programmable interactions.
According to scientists at D-Wave, this work is important in the following regards:
* The demonstration of phase transitions as a function of quantum mechanical energy scale is strong evidence that the D-Wave quantum system is able to perform quantum simulations.
* The results demonstrate that the embedded 3-dimensional system, whose connectivity is vastly different from that of the physical layout of qubits within the QPU, behaves as expected.
*The experimental techniques used in this study have motivated new work to search for signatures of long-range correlations between quantum mechanical degrees of freedom in the vicinity of the observed phase transitions. Such correlations are not only of scientific interest, but are expected to be critical to realizing a computational advantage when using D-Wave’s quantum computers on a broad range of computation problems of commercial utility.
“This work represents an important milestone for quantum computing, because it is the first time physics of this kind has been simulated in a scalable architecture at such a large scale,” said Vern Brownell, CEO of D-Wave. “It also provides unprecedented validation for annealing quantum computing, which is the basis of D-Wave’s quantum technology.”
A practical large-scale quantum computer will be a key enabling technology for advancing many branches of sciences and engineering.
Simulating correlated electron systems
Correlated electron systems are generally difficult to simulate because of limited capabilities of computational resources. Harris et al. used a D-Wave chip based on a large array of superconducting elements to simulate the phases of a complex magnetic system. They tuned the amount of frustration within the lattice and varied the effective transverse magnetic field, which revealed phase transitions between a paramagnetic, an ordered antiferromagnetic, and a spin-glass phase. The results compare well to theory for this spin-glass problem, validating the approach for simulating problems in materials physics.
Abstract – Phase transitions in a programmable quantum spin glass simulator
Understanding magnetic phases in quantum mechanical systems is one of the essential goals in condensed matter physics, and the advent of prototype quantum simulation hardware has provided new tools for experimentally probing such systems. We report on the experimental realization of a quantum simulation of interacting Ising spins on three-dimensional cubic lattices up to dimensions 8 × 8 × 8 on a D-Wave processor (D-Wave Systems, Burnaby, Canada). The ability to control and read out the state of individual spins provides direct access to several order parameters, which we used to determine the lattice’s magnetic phases as well as critical disorder and one of its universal exponents. By tuning the degree of disorder and effective transverse magnetic field, we observed phase transitions between a paramagnetic, an antiferromagnetic, and a spin-glass phase.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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