Silicon quantum computer fidelity has made an important breakthrough

The British journal Nature published three papers in a row on the 19th, and scientists from three teams made important breakthroughs in the development of fault-tolerant quantum computers. They verified the fidelity of the silicon double qubit gate, exceeding the threshold of fault-tolerant computers (99%). The results confirm that powerful and reliable quantum computing in silicon materials is becoming a reality. The study also shows that silicon quantum computers, like superconductivity and ion traps, are promising candidates for large-scale quantum computer development.

A research team at the University of New South Wales in Australia created a double qubit universal quantum logic operation between two nuclear spins formed by a phosphorus donor, which was introduced into the silicon using an industry-standard ion implantation method. Using a method known as "quantum gate set tomography (GST)," they validated the performance of their quantum processors, achieving up to 99.95 percent single qubit fidelity and 99.37 percent dual qubit fidelity. In addition, according to the results of the study, the electron spin itself is a qubit that can be entangled with two atomic nuclei to form a three-qubit quantum entanglement state, which reaches 92.5% fidelity. This paves the way for the manufacture and application of large silicon-based quantum processors in the real world.

Three lead authors of the paper from a research team from the University of New South Wales in Australia. Image source: Eurekalert website

The delft University of Technology research team in the Netherlands used materials formed from stacks of silicon and silicon germanium alloys to create a dual qubit system in which quantum information is encoded in electron spins confined to quantum dots, ultimately achieving 99.87% single qubit fidelity and 99.65% double qubit fidelity.

The research team at the Riken Institute of Physicochemistry in Japan took a similar route, using the same stack of materials produced by delft's team, creating two-electron qubits that achieved 99.8 percent single qubit fidelity and 99.5 percent double qubit fidelity. The results of the study allowed the spin qubits to compete with superconducting circuits and ion traps in terms of general-purpose quantum control performance.

In the course of a collaborative experiment, a team of researchers from the Netherlands and Japan discovered that a property called rabbinic frequency is key to the performance of quantum computer systems. They also found a frequency range with a single qubit gate fidelity of 99.8% and a double qubit gate fidelity of 99.5%, reaching the desired threshold.

The researchers demonstrated that they can achieve general-purpose operations, which means that all the fundamental operations that make up quantum operations, including single-qubit operations and double-qubit operations, can be performed at gate fidelity above the error correction threshold.

To test the performance of the new system, the researchers also employed the dual-qubit Deutsch-Jozsa algorithm and the Grover search algorithm. Both algorithms can output correct results with 96%-97% high fidelity, indicating that silicon quantum computers can perform high-precision quantum computing.

Editor-in-chief dots

Currently, the world is in the midst of a race to develop large-scale quantum computers, but scientists' efforts are hampered by factors such as the decoherence problem, the noise generated in qubits. This problem becomes more serious as the number of qubits increases, hindering scale expansion. So, to enable an applicable large computer, scientists set at least 99 percent double qubit gate fidelity. Now that this has been achieved on some types of computers, it can be argued that scientists are crossing the key challenges facing silicon quantum computers.

Source: Science and Technology Daily