The University of Maryland has created the largest quantum simulation using 53 trapped-ion qubits. It is the largest quantum simulation ever performed with high- efficiency single-shot measurements of individual qubits. This provides access to arbitrary many-body correlators that carry information that is difficult or impossible to model classically. This experimental platform can be extended to tackle provably hard quantum problems such as Ising sampling. Given an even higher level of control over the interactions between spins, as already demonstrated for smaller numbers of trapped-ion qubits, this same system can be upgraded to a universal quantum computer.
A quantum simulator is a type of quantum computer that controls the interactions between quantum bits (or qubits) in a way that can be mapped to certain quantum many-body problems. As it becomes possible to exert more control over larger numbers of qubits, such simulators will be able to tackle a wider range of problems, such as materials design and molecular modeling, with the ultimate limit being a universal quantum computer that can solve general classes of hard problems3. Here we use a quantum simulator composed of up to 53 qubits to study non-equilibrium dynamics in the transverse-field Ising model with long-range interactions. We observe a dynamical phase transition after a sudden change of the Hamiltonian, in a regime in which conventional statistical mechanics does not apply. The qubits are represented by the spins of trapped ions, which can be prepared in various initial pure states. We apply a global long-range Ising interaction with controllable strength and range, and measure each individual qubit with an efficiency of nearly 99 per cent. Such high efficiency means that arbitrary many-body correlations between qubits can be measured in a single shot, enabling the dynamical phase transition to be probed directly and revealing computationally intractable features that rely on the long-range interactions and high connectivity between qubits.
Harvard’s 51 atom quantum simulator
Harvard’s simulator uses 51 rubidium atoms held in place with a hundred lasers.
Lasers are as fine optical tweezers. Lasers pluck individual atoms out of the vapor and trap them in place. And they allow the Harvard team to finely program their device, arranging the atoms into exactly the setup they want to test, before they begin their simulation.
The whole system cools to near-absolute zero,
The machine again strikes the atoms with lasers. The atoms become excited and enter a Rydberg state.
In a Rydberg state, the atoms don’t get smeared between two points. Instead, they swell.
In a Rydberg state, the electrons swing wider and wider, farther and farther away from the core of the atoms — until they cross paths with the other atoms in the computer simulation. All these wildly excited atoms suddenly find themselves sharing the same space, and interact with one another as quantum magnets that the researchers can observe.
Controllable, coherent many-body systems can provide insights into the fundamental properties of quantum matter, enable the realization of new quantum phases and could ultimately lead to computational systems that outperform existing computers based on classical approaches. Here we demonstrate a method for creating controlled many-body quantum matter that combines deterministically prepared, reconfigurable arrays of individually trapped cold atoms with strong, coherent interactions enabled by excitation to Rydberg states. We realize a programmable Ising-type quantum spin model with tunable interactions and system sizes of up to 51 qubits. Within this model, we observe phase transitions into spatially ordered states that break various discrete symmetries, verify the high-fidelity preparation of these states and investigate the dynamics across the phase transition in large arrays of atoms. In particular, we observe robust many-body dynamics corresponding to persistent oscillations of the order after a rapid quantum quench that results from a sudden transition across the phase boundary. Our method provides a way of exploring many-body phenomena on a programmable quantum simulator and could enable realizations of new quantum algorithms