Google has created a new kind of quantum computer by marrying together two previous approaches to building these exotic devices. The new machine can simulate the behaviour of magnets in such detail that it could help physicists rewrite their understanding of magnetism.
The tech giant has been building quantum computers for a number of years. In 2019, Google demonstrated for the first time that such a device could run an algorithm that would be impossible for a conventional supercomputer to tackle. These digital quantum computers can be thought of as quantum versions of ordinary, classical computers, and it is hoped that they will one day be able to solve certain real-world problems exponentially faster.
Another kind of quantum computer, called a quantum simulator, instead simulates real-world quantum systems, like a magnet or crystal, in more detail than is possible with a classical computer. These analogue quantum computers are generally only useful for specific tasks, rather than being broadly programmable like their digital counterparts, and can be difficult to control.
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Now, researchers at Google have combined the two approaches by using the qubits, or quantum bits, of a digital quantum computer to model a two-dimensional magnet. Rather than using the qubits to perform logical operations one by one, Google had them operating all at the same time, mimicking a real-world magnet whose atoms are flipping their magnetic state and interacting all at once as energy is added to the system.
Using digital qubits, which gives researchers fine control and an ability to make more precise measurements, to run an analogue simulation, which very quickly creates complex quantum states, combines useful features of both approaches, says at University College London. 鈥淵ou didn鈥檛 really have that much control on the types of problems that you could simulate [using analogue machines], but combining the analogue simulation with digital preparation of states is tremendously powerful.鈥�
Our current understanding of certain magnet systems says that the speed at which the energy of a system is increased dictates how interlinked the atoms become, but Google found that its simulations deviated from this theoretical prediction. The company declined to comment on the work.
This anomaly could be of interest to theoretical physicists, says Green, but it will need to be more closely examined to make sure the quantum computer simulation matches real-world systems.
Being able to reliably extract quantitative information about these simulated systems means you can test your theoretical calculations and hone your theories, says at the University of Oxford.
鈥淲hat excites me on the basic science level is the potential with quantitative quantum simulation to be able to take different approximate theories and really go and say, 鈥橶ell, this one does properly predict what we see in the experiment and this one doesn鈥檛鈥�,鈥� says Daley. 鈥淭hat can give us deep insights into what鈥檚 happening in these systems.鈥�
arXiv
