A team of scientists at Yale University has experimentally demonstrated one of the key steps in building the architecture for quantum computers — the ‘teleportation’ of a quantum gate between two logical qubits, on demand.
A quantum computer has the potential to efficiently solve problems that are intractable for classical computers.
However, constructing a large-scale quantum processor is challenging because of the errors and noise that are inherent in real-world quantum systems.
One approach to addressing this challenge is to utilize modularity — a strategy used frequently in nature and engineering to build complex systems robustly.
“A quantum modular architecture consists of a collection of modules that function as small quantum processors connected into a larger network,” explained team leaders Professor Robert Schoelkopf and Dr. Kevin Chou and their colleagues.
“Modules in this architecture have a natural isolation from each other, which reduces unwanted interactions through the larger system.”
“Yet this isolation also makes performing operations between modules a distinct challenge. Teleported gates are a way to implement inter-module operations.”
Using a theoretical protocol developed in the 1990s, Professor Schoelkopf, Dr. Chou and co-authors demonstrated a quantum operation, or ‘gate,’ without relying on any direct interaction.
“Our work is the first time that this protocol has been demonstrated where the classical communication occurs in real-time, allowing us to implement a ‘deterministic’ operation that performs the desired operation every time,” Dr. Chou said.
“Quantum calculations are done via delicate bits of data called qubits, which are prone to errors,” Professor Schoelkopf added.
“In experimental quantum systems, ‘logical’ qubits are monitored by ‘ancillary’ qubits in order to detect and correct errors immediately.”
“Our experiment is also the first demonstration of a two-qubit operation between logical qubits.”
“It is a milestone toward quantum information processing using error-correctable qubits.”
The team’s results are published in the journal Nature.
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Kevin S. Chou et al. Deterministic teleportation of a quantum gate between two logical qubits. Nature, published online September 5, 2018; doi: 10.1038/s41586-018-0470-y