Researchers at Yale University have demonstrated one of the key steps in the design of modular quantum computers: the deliberate "teleportation" of a quantum gate between two qubits.
The research is published in the journal Nature. The main principle of this work is quantum teleportation, a unique property of quantum mechanics, previously used to transfer unknown quantum states between two parties without physically sending the state itself. Using a theoretical protocol developed in the 1990s, Yale scientists experimentally demonstrated a quantum operation - a gate - without any direct interactions. Such gates are necessary for quantum computing, which relies on networks of individual quantum systems - an architecture that many researchers believe can compensate for the errors inherent in quantum computing processors.
A team led by lead researcher Robert Schoelkopf and former graduate student Kevin Chow is exploring a modular approach to quantum computing. The modularity inherent in everything from the organization of the biological cell to the engines of SpaceX's latest rockets has proven to be an effective strategy in building large, complex systems. A quantum modular architecture consists of a set of modules that function as small quantum processors connected to a larger network.
The modules in this architecture are naturally isolated from each other, which prevents unwanted interactions across larger systems. However, this isolation also complicates transactions between modules. Teleported gates are a way of performing inter-module operations.
An overview of the modular quantum architecture network in a new study.
“Our work was the first time that this protocol was demonstrated, where classical communication occurs in real time, which allows for a 'deterministic' operation that performs the necessary process every time,” says Chow.
Fully functioning quantum computers have the potential to achieve computational speeds orders of magnitude higher than those of today's supercomputers. Yale scientists are at the forefront of research to develop the first fully functional quantum computers and have already done groundbreaking work in quantum computing with superconducting circuits.
Quantum computing is done with sensitive bits of data known as qubits, which are error prone. In experimental quantum systems, "logical" qubits are controlled by "auxiliary" qubits for registration and instant error correction.
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“Our experiment is the first demonstration of a two-qubit operation between logical qubits,” says Schoelkopf. "This is a milestone on the path to processing quantum information with error-correcting qubits."
Vladimir Guillen
