Quantum Hardware Quantum Physics

Researchers produce Quantum Dots for reduced error Quantum Computing

December 31, 2020

A team of researchers at CEA-Leti in France and the University of Copenhagen’s Niels Bohr Institute have made 2D arrays on a 300mm CMOS wafer to boost quantum computers.

The device has a 2×2 quantum dot lattice on a commercial foundry service, and the array is designed to reduce errors in quantum computer architectures by improving upon the error correction systems.

The potential of these quantum dots is immense

‘What we have shown is that we can realize single electron control in every single one of these quantum dots. This is very important for the development of a qubit, because one of the possible ways of making qubits is to use the spin of a single electron. Reaching this goal of controlling the single electrons and doing it in a 2D array of quantum dots was very important for us.’

Fabio Ansaloni, a researcher at the centre for Quantum Devices at NBI

To improve quantum error correction routines, researchers can extend the processors of the machines. Through the use of quantum error correction, future quantum computers can become fault tolerant when individual qubits fail mid-computation.

‘The original idea was to make an array of spin qubits, get down to single electrons and become able to control them and move them around. In that sense it is really great that Leti was able to deliver the samples we have used, which in turn made it possible for us to attain this result. A lot of credit goes to the pan-European project consortium, and generous funding from the EU, helping us to move from the level of a single quantum dot with a single electron to having two electrons, and now moving on to the two dimensional arrays. Two dimensional arrays is a really big goal, because that’s beginning to look like something you absolutely need to build a quantum computer. So Leti has been involved with a series of projects over the years, which have all contributed to this result.’

Anasua Chatterjee, assistant professor at NBI

Earlier in 2015, some researchers in Grenoble were ablew to make the first spin qubit, only it was not based on electrons, but holes. The current quantum dots are three times more powerful.

‘The scalability of a modern, industrial process is essential as we start to make bigger arrays, for example for small quantum simulators. Second, when making a quantum computer, you need an array in two dimensions, and you need a way of connecting the external world to each qubit. If you have 4-5 connections for each qubit, you quickly end up with a (sic) unrealistic number of wires going out of the low-temperature setup. But what we have managed to show is that we can have one gate per electron, and you can read and control with the same gate. And lastly, using these tools we were able to move and swap single electrons in a controlled way around the array, a challenge in itself.’

Anasua Chatterjee, assistant professor at NBI

The first order of business is to control the errors that occur when quantum computers are performing tasks. However, current qubits still have higher error rates. With the 2D quantum dot array, the qubits can check on each other when enough are combined.

The NBI research has shown that controlling single electrons is now a reality, as well as controlling them without a magnetic field present. The next step is to look for spins, or spin signatures, when there is a magnetic field present.

These results will be important when single and two-qubit gates are implemented between the single qubits in the array. A complete set of quantum gates is theoretically capable of universal quantum computation as well.

See the Original Research Paper