The research, published in the journal Nature, was led by researchers at Princeton University in collaboration with colleagues at the University of Konstanz in Germany and the Joint Quantum Institute, which is a partnership of the University of Maryland and the National Institute of Standards and Technology.
Researchers from two teams now working with Intel have reported advances in a new quantum computing architecture, called spin qubits.They’re obviously not the full-purpose quantum computers of the future. But they’ve got a major selling point over other quantum computing designs.
Quantum computers, for the uninitiated, turn the rules of computers on their head like the Wizard of Oz going from black-and-white to color. Classical computers perform all of their calculations by converting data into binary code. Each zero or one is represented by some physical two-choice bit. Quantum computers instead use “qubits”—quantum bits that take on the two values simultaneously during calculations. Pairs of qubits talk to one another using the rules of quantum mechanics. They output regular bit values once the user needs an answer.
There are lots of ways to physically construct qubits. It requires building a collection of two-state systems that operate and communicate via the rules of quantum mechanics. Google and IBM use tiny pieces of supercooled, superconducting electronics. IonQ hopes to use atoms trapped by lasers, with two different internal states representing the two qubit states. Microsoft hopes to use some pretty out-there, still unobserved physics. But there are other ways.
Today, a research group at TU Delft, called QuTech, announced that they’d successfully tested two “spin qubits” on hardware supplied by researchers from the University of Wisconsin, Madison. These qubits involve the interaction of two confined electrons in a silicon chip. Each electron has a property called spin, which sort of turns it into a tiny magnet, with two states: “up” and “down.” The researchers control the electrons with actual cobalt magnets and microwave pulses. They measure the electron’s spins by watching how nearby electric charges react to the trapped electrons’ movements.
Those researchers, now working in partnership with Intel, were able to perform some quantum algorithms, including the well-known Grover search algorithm (basically, they could search through a list of four things), according to their paper published today in Nature. Additionally, a team of physicists led by Jason Petta at Princeton reported in Nature that they were able to pair light particles, called photons, to corresponding electron spins. This just means that distant spin qubits might be able to talk to one another using photons, allowing for larger quantum computers.
There are some advantages to these systems. Present-day semiconductor technology could create these spin qubits, and they would be smaller than the superconducting chips used by IBM. Additionally, they stay quantum (meaning they can maintain their ability to hold simultaneous values) longer than other systems.
Both of these papers report on research done in dilution refrigerators, similar to those used for superconducting qubits,But there may be a future where these operate at room temperature, unlike superconducting qubits. You can also contrast this with ion-based quantum computers, which require ultra-high vacuum and multiple control lasers to operate.
There are drawbacks. Since these qubits are so isolated, it’s very difficult to measure these spins, and even more difficult to get them to interact with each other. That’s why gate times have been historically slow for these systems.” Qubits needed to be really close to each other,That will enable longer-range interactions, like qubits talking to ones further away on the same chip or even on another chip.
It is a big milestone in the quest of building a truly powerful quantum computer as it opens up a pathway for cramming hundreds of millions of qubits on a square-inch chip. These are very exciting developments for the field and beyond.
We’re still in a sort of foggy early era of quantum computers, where systems of less than a thousand qubits can only make pretty limited calculations.