Usually quantum computers are devices that can fill entire laboratories. Now a compact prototype quantum computer can fit in two 19-inch server racks like those found in data centers throughout the world, which could help improve battery designs or crack codes, a new study finds.
A quantum computer with enough components known as quantum bits or "qubits" could in theory achieve a "quantum advantage" enabling it to find the answers to problems no classical computer could ever solve.
However, given how the most advanced current quantum computers typically only have a few dozen qubits at most yet fill up whole rooms. As such, scaling up to hundreds of qubits for practical applications is often thought to prove a challenging task.
Now scientists in Austria and their colleagues have developed a 24-qubit quantum computer that altogether fits in a pair of boxes that are each, at 1.7 cubic meters in size, about as large as a studio apartment's shower. They each require a standard wall-mounted electric socket, consuming less than 3.7 kilowatts per rack.
"From a research point of view, the underlying physics is not new," says study senior author Thomas Monz, a quantum physicist at the University of Innsbruck in Austria. Monz is also the cofounder and CEO of Alpine Quantum Technologies, a spinoff of the University of Innsbruck and the Austrian Academy of Sciences. "It's really been about the engineering to bring quantum one step closer to general use in general environments."
The device uses positively charged calcium ions trapped within electric fields as its qubits. Laser pulses manipulate the ions and link the qubits together in a quantum phenomenon known as entanglement. The machine is housed in a series of aluminum modules that stack on top of each other inside two server racks.
In a lab, a quantum computer's parts are usually spread out horizontally "and thus takes up lots of space," Monz says. Much of the way in which the researchers shrunk a quantum computer to a compact size involved talking with suppliers to see what could fit within a 19-inch server rack — for example, an ion trap from Alpine Quantum Technologies that requires just a fraction of the space of comparable devices, he says. The rest involved ensuring they could shield the qubits from vibrations, magnetic field fluctuations and other disturbances at a similar level as in a lab, he adds.
The scientists noted their machine performs at least on par with similar lab-scale setups. Indeed, the device could generate the largest maximally entangled state yet generated in any quantum computer.
"It's compact, but it's not any less versatile," Monz says. Potential applications include quantum chemistry experiments, which can test the performance of lithium batteries and eventually find new drugs, as well as cracking standard encryption techniques, he says.
The new quantum computer will soon be programmable online using a number of quantum computing languages, such as Google's Cirq, IBM's Qisket, Cambridge Quantum Computing's tket, and Xanadu's PennyLane, Monz says. Academic researchers can contact the University of Innsbruck, whereas commercial customers can contact Alpine Quantum Technologies.
Monz notes they could make their quantum computer even more compact. "I don't see why we shouldn't be able to get it down to a larger desktop PC level, or maybe two of them, in terms of volume," he says. Indeed, "the device could become mobile — in particular, due to the low power consumption."
This advance is the latest example of a quantum computing trend towards shrinking. For instance, recently the Australian-German startup Quantum Brilliance revealed it had developed a diamond-based quantum computer the size of a server module. Although its first-generation device only hosts 5 qubits, it says in five years time it will boast 50-plus qubits and shrink to the size of a graphics card.
Next year, Monz and his colleagues aim to scale up to 50 qubits. "All quantum processors, to date, are too small with respect to the number of qubits," Monz says. "We all need to push for hundreds and thousands of qubits, while maintaining and increasing the level of performance. We'll see how we can do that, while maintaining a sufficiently small footprint."
The aim is to integrate the new quantum computer with conventional server farms. Scaling the device up to more qubits could help it outcompete conventional high-performance computing (HPC) sites while not requiring "the power of a village," Monz says. "You may also call our quantum computer a green alternative to HPC."
Monz and his colleagues detailed their findings online June 17 in the journal PRX Quantum.