According to a paper published in the journal Nature on the 25th, the team led by Thomas Muntz of the Department of experimental physics of Innsbruck University in Austria, Marcus Muller of Aachen University of technology in Germany and the research center of Zurich in Germany showed the basic building blocks of fault-tolerant quantum computing, and successfully realized a set of computing operations on two logical qubits for the first time, which can be used to realize any possible operation, It means that error free quantum computers may become a reality.
Quantum computers are inherently more susceptible to interference from the environment, so error correction mechanisms may always be needed, otherwise errors will spread uncontrolled in the system and information will be lost. The quantum non cloning theorem shows that it is impossible to replicate any unknown quantum state exactly. Therefore, redundancy can be realized by allocating logical quantum information to the entangled states of multiple physical systems, such as multiple individual atoms.
"For quantum computers in the real world, we need a set of general gates with which we can program all algorithms," explained Lucas posler, an experimental physicist in Innsbruck
The team implemented the universal gate set on an ion trap quantum computer with 16 trapped atoms. Quantum information is stored in two logical qubits, each of which is distributed over seven atoms.
Now, for the first time, researchers can implement two calculation gates on these fault-tolerant qubits, which is necessary for the general gate set: a gate (a control not gate) and a logic t gate that act on two qubits, which is particularly difficult to implement on fault-tolerant qubits.
Physicists demonstrated the T-gate by preparing a special state in a logical qubit and transmitting it to another qubit through entanglement gate operation.
In the encoded logical qubits, the stored quantum information is protected from errors. But if there is no calculation operation, it is useless, and these operations themselves are easy to make mistakes. Therefore, researchers operate on logical qubits, so that errors caused by underlying physical operations can be detected and corrected. Therefore, they implemented the fault-tolerant implementation of the first general gate set on the encoded logical qubits.
The implementation of fault tolerance requires more operations than non fault tolerance. This will introduce more errors on the scale of a single atom. The workload and complexity have increased, but the resulting quality is better. The researchers also used numerical simulations on classical computers to check and confirm their experimental results.
Researchers have demonstrated all the foundations of fault-tolerant computing on quantum computers. The task now is to implement these methods on larger and more useful quantum computers. This method demonstrated on ion trap quantum computer can also be used in the architecture of other quantum computers.