How large does a useful quantum computer need to be?

This is an important but surprisingly hard question to answer.

Sept 28 (Reuters) - PsiQuantum is aiming to deliver its first commercial quantum computing system in under six years, its CEO said as the startup announced a partnership with the U.S. Department of Energy to develop advanced fridges for its machines…

PsiQuantum to start installation of its cryogenic quantum modules, each containing photonic quantum hardware, into SLAC’s LCLS-II cryoplant facility, capable of kilowatts of cooling power. This partnership accelerates the development and testing of this novel technology while also defining opportunities for further collaboration in the future.

Cracking cryptographic protocols is a well-known impact area for fault-tolerant quantum computing. Clearly it is important to estimate just when quantum computers will impact cryptography.

On the outskirts of Santa Barbara, California, between the orchards and the ocean, sits an inconspicuous warehouse, its windows tinted brown and its exterior painted a dull gray. The facility has almost no signage, and its name doesn’t appear on Google Maps.

A 1960s nuclear research lab in the North of England will host a new quantum computing facility under plans drawn up by a Silicon Valley technology company.

PsiQuantum is to set up a research hub at the Daresbury Laboratory in Cheshire, using the facility’s state of the art cooling systems to develop its technology.

The emerging technology of quantum computing could revolutionize the fight against climate change, transforming the economics of decarbonization and becoming a major factor in limiting global warming to the target temperature of 1.5°C (see sidebar “What is quantum computing?”).

DARPA, the Defense Advanced Research Projects Agency, has announced that it has selected the companies that will receive funding under its Underexplored Systems for Utility-Scale Quantum Computing (US2QC) program.

In 2009, Jeremy O'Brien, a professor at the University of Bristol, published a research paper describing how to repurpose on-chip optical components originally developed by the telecom industry to manipulate single particles of light and perform quantum operations. By 2016, based on the earlier photonic research, O’Brien and three of his academic colleagues, Terry Rudolph, Mark Thompson, and Pete Shadbolt, created PsiQuantum.