One of the key concepts of quantum physics is entanglement, in which two or more quantum systems become so inextricably linked that their collective state can not be determined by observing each element individually. Now, Yale researchers have developed a "universal packer" that can bind a variety of encoded particles on demand.
The discovery represents a powerful new mechanism with potential uses in quantum computing, cryptography and quantum communications. The research is led by Robert Schoelkopf's Yale laboratory and appears in the journal Nature.
Quantum calculations are performed with delicate data called qubits, which are prone to errors. To implement faithful quantum computing, scientists say, they need "logical" qubits whose errors can be detected and corrected using quantum error correction codes.
"We've shown a new way to create ports between logically encoded qubits that can eventually be corrected for errors," said Schoelkopf, the professor of applied physics and physics at Yale and director of the Yale Quantum Institute. "It's a much more sophisticated operation than it was previously."
The interleaving mechanism is called the exponential-SWAP port. In the study, the researchers demonstrated the new technology by determining the coded states deterministically in any chosen configurations or codes, each housed in two otherwise isolated superconducting 3D microwave cavities.
"This universal setback is critical to robust quantum computing," said Yvonne Gao, co-lead author of the study. "Scientists have invented a large number of hardware-efficient quantum error correction codes – each one intelligently designed with unique features that can be exploited for different applications. However, each of them requires the installation of a new set of custom operations, introducing significant hardware overhead and reduced versatility. "
The universal packer attenuates this limitation by providing a port between the desired input states. "Now we can choose any desired code or even change them quickly without having to re-spin the operation," said co-first author Brian Lester.
The discovery is just the latest step in Yale's quantum research work. Yale scientists are at the forefront of efforts to develop the first fully useful quantum computers and have done pioneering work on quantum computing with superconducting circuits.
Additional authors of the study are Kevin Chou, Luigi Frunzio, Michel Devoret, Liang Jiang and Steven Girvin. The research was supported by the US Army Research Office.
Publication: Yvonne Y. Gao, et al., "Entanglement of bosonic modes through a projected exchange interaction", Nature volume 566, pages 509-512 (2019)