One day quantum computers will work miracles, from breaking digital encryptions to designing wonder drugs. The advantage of many quantum algorithms is still speculative at this early stage. Some researchers are wondering if it is possible to control the particles at the level. A physicist at Harvard University said it was a very daunting goal.
Physicists are using more specialized machines called quantum simulators to emulate the behavior of quantum systems, even though they don't have a full-blown quantum computer.
If you want to make a simulation of nature, you would better make it quantum mechanical, as Richard Feynman said in a 1981 lecture.
In the past few years, groups in Paris and Cambridge, Massachusetts, have made great progress using a dark horse type of quantum simulator. A series of simulations would take months or more to replicate on a classical computer.
Ivan Deutsch is a pioneer of the technology and is currently at the University of New Mexico.
Today the Cambridge group unveiled their most significant discovery yet, the detection of an elusive state of matter known as a quantum spin liquid, which exists outside the century-old paradigm outlining the ways in which matter can organize. It confirms a theory that has been around for nearly 50 years. It is a step towards the goal of building a universal quantum computer.
Ehud Altman, a Condensed Matter theorist at the University of California, Berkeley, said that the ultracold atomic experiment was one of the most impressive and ground-breaking experiments in the field.
There are promising ideas in science and mathematics. Join the conversation with us.
Staying neutral.
A new approach to quantum computing uses neutral atoms. Although the method lags behind more popular quantum computing technologies, neutral atoms have special properties that have captured the imaginations of quantum engineers.
The key to building a quantum computer is to assemble a collection of qubits that satisfy two conflicting requirements. If the qubits are not protected from the outside world, they will be destroyed. They must both be accessible and manipulable.
Proponents say neutral atoms balance these demands well. Laser beams can protect atoms from interference. An additional laser pulse can cause atoms to become larger than a classical bit. The neutral atom qubits can assume large and small positions at the same time, and can connect with one another throughentanglement, two essential ingredients for quantum computing.
Researchers have been controlling neutral atoms for two decades. In 2001, groups grabbed single atoms with lasers, then entangled pairs of atoms in 2010. The groups in Cambridge and Paris were able to wrangle a lot of atoms. The next-gen machines are capable of being powerful simulations of quantum phenomena.
The difference between 100 or 50 qubits and 256 qubits is referred to as the difference between 100 or 50 qubits. That matters.
The grids of neutral atoms are being used to probe quantum matter. These are like the familiar phases of liquid and solid but with more exotic and complicated configurations that can be accomplished by throwing superposition and entanglement into the mix. Understanding what causes high-temperature superconductivity is one of the practical applications of the exploration of quantum phases.
Condensed-matter physicists study phases using nature's crystals and what they can grow in their labs. The neutral atom researchers can program their matter by positioning the atoms into lattices of any shape and engineering atomic interactions through the manipulation of the rydberg states.
The leader of the Cambridge group said that they assemble an artificial crystal.
The Cambridge and Paris groups used a textbook theory of magnetism, the quantum Ising model, for the first time, to measure how pockets of magnetism grow and shrink with changing temperature. It would have taken months to do the simulations on a classical computer. The experimental apparatus is at a point where it becomes impractical to try to mimic it. The teams described their simulations in Nature.
The Cambridge collaboration consists of a team at Harvard, a lab at Harvard, and a group at the Massachusetts Institute of Technology.
In 1973, Philip Anderson predicted that matter might enter a strange state called a quantum spin liquid. Many atoms have a property known as spin. Spins point in opposite directions at low temperatures because they interact magnetically. Only two of the three atoms can point in opposite directions if they are arranged in a triangle. A trianglelike lattice of atoms can't be neatly arranged. The spins are similar to how atoms move in a liquid.
There is a lot of entanglement in quantum spin liquids. Individual particles can sense the system's overall topology, which leads to "topological" order. If you punch a hole in an ice cube it will stay frozen, but the atoms at the center of the quantum spin liquid could change the system's properties. That makes quantum spin liquids a new class of matter.
The mineral Herbertsmithite has a crystal structure that is frustrating to atoms and has indirect hints of quantum spin liquids. It is not possible to directly confirm a material's status as a quantum spin liquid.
The group used the quantum simulator to see something. The neutral atoms were programmed to act like the atoms in Herbertsmithite. They measured the rydberg states throughout loops and strings of atoms. The first direct measurement of the order of a quantum spin liquid was made.
The amazing thing is that it looks very convincing, according to Altman.
The fractional quantum hall effect was the first clear-cut discovery of a topologically ordered phase of matter. Researchers are getting control over a second example.
In my view, this is a very special moment.
Scaling up
Both neutral atom groups have launched spinoff businesses, and QuEra Computing in Cambridge has raised $17 million from investors, including the Japanese communications and e-commerce.
The companies hope to turn their simulators into universal quantum computers that can handle any quantum calculation. Control over individual atoms is required to use them as qubits. While not as mature as the quantum computers from IBM and Google, neutral atoms may still catch up. Greiner said that sometimes he starts to get skeptical. Even with a few atoms, we can do things that no computer can calculate.
