2021-09-14

Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips

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Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips

Scanning electron microscope (pseudo-color) image of the new device, from: RIKEN.

It is reported that quantum computers use peculiar principles of quantum physics to greatly increase the processing power and speed of computers. Relevant information is stored in a “bit” method similar to that of a traditional computer, but the “qubit” also has some unexpected manipulation methods.

Thanks to the “quantum entanglement” feature, when you check the properties of one of the particles, you can infer the properties of one (or more) partner particles, and the particles in the entangled state no matter how far apart The distance will be affected by the correspondence.

Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips(1)

Research Picture-1: Equipment and Experiment Settings

In quantum computers, entangled qubits enable data to be transmitted and processed faster, and improve error correction. And most of the time, qubits are entangled in pairs. But now, the RIKEN research team has discovered the three-qubit entangled state on silicon for the first time.

In this case, qubits are composed of small silicon circles called quantum dots. As one of the main candidates for qubits in quantum computers, silicon chips have been widely used in electronic products.

But more importantly, these quantum dots are stable for a long period of time, can be precisely controlled, operate at higher temperatures, and can be scaled relatively easily.

The three-qubit entangled state can better achieve this goal, and previous studies have successfully entangled three photons together. Only so far, the industry has always believed that they are beyond reach.

Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips(2)

Research Picture-2: Single Qubit / Controlled Phase Operation

Seigo Tarucha, the first researcher, said: “The two-qubit operation is sufficient to perform basic logic calculations, but the three-qubit system is the smallest unit of error correction that is enlarged.”

The good news is that the three-quantum dot device created by the RIKEN Institute of Emerging Materials has achieved a unique operation through the aluminum gate control.

Each quantum dot contains an electron, which can represent binary 0 or 1 through its spin state, regardless of whether it is up or down at a given time.

In addition, the magnetic field gradient keeps the resonance frequencies of the qubits separated, thus supporting their individual addressing.

Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips(3)

Research Picture-3: Three Qubits Entanglement generation and measurement

In order to entangle three qubits together, the research team first used a quantum computer public unit called a “double qubit gate”, and then combined the third qubit with the The doors are entangled.

The resulting three-qubit array has 88% high fidelity, indicating the probability that the qubit is in the “correct” state during measurement. The research team added: This powerful entanglement can be used well for error correction.

Because in quantum computers, qubits tend to randomly flip states and lose their stored information. The correction method that works well on traditional computers is not suitable for novel quantum systems.

In contrast, other quantum chip designs need to use a grid of nine qubits to monitor each other, and IBM’s error correction solution uses non-entangled qubits to check neighboring qubits. status.

Scientists from the Japanese Institute of Physics and Chemistry discover three-qubit entangled states on silicon chips(4)

Looking forward, the RIKEN research team also hopes to use A three-qubit device to demonstrate the original error correction and manufacture a device with 10 (or more) qubits.

Seigo Tarucha said that they plan to develop 50-100 qubit devices and apply more complex error correction protocols to lay the foundation for the manufacture of large-scale quantum computers within ten years.

Details about this research have been published in the journal Nature Nanotechnology.