For quantum computer systems to surpass their classical counterparts in pace and capability, their qubits — that are superconducting circuits that may exist in an infinite mixture of binary states — have to be on the identical wavelength. Reaching this, nonetheless, has come at the price of dimension. Whereas the transistors utilized in classical computer systems have been shrunk right down to nanometer scales, superconducting qubits lately are nonetheless measured in millimeters — one millimeter is one million nanometers.
Mix qubits collectively into bigger and bigger circuit chips, and you find yourself with, comparatively talking, an enormous bodily footprint, which suggests quantum computer systems take up a number of bodily area. These should not but gadgets we are able to carry in our backpacks or put on on our wrists.
To shrink qubits down whereas sustaining their efficiency, the sphere wants a brand new strategy to construct the capacitors that retailer the vitality that “powers” the qubits. In collaboration with Raytheon BBN Applied sciences, Wang Fong-Jen Professor James Hone’s lab at Columbia Engineering lately demonstrated a superconducting qubit capacitor constructed with 2D supplies that is a fraction of earlier sizes.
To construct qubit chips beforehand, engineers have had to make use of planar capacitors, which set the mandatory charged plates facet by facet. Stacking these plates would save area, however the metals utilized in typical parallel capacitors intrude with qubit data storage. Within the present work, printed on November 18 in Nano Letters, Hone’s PhD college students Abhinandan Antony and Anjaly Rajendra sandwiched an insulating layer of boron nitride between two charged plates of superconducting niobium dieselenide. These layers are every only a single atom thick and held collectively by van der Waals forces, the weak interplay between electrons. The group then mixed their capacitors with aluminum circuits to create a chip containing two qubits with an space of 109 sq. micrometers and simply 35 nanometers thick — that is 1,000 instances smaller than chips produced beneath typical approaches.
After they cooled their qubit chip down to simply above absolute zero, the qubits discovered the identical wavelength. The group additionally noticed key traits that confirmed that the 2 qubits have been changing into entangled and appearing as a single unit, a phenomenon often known as quantum coherence; that might imply the qubit’s quantum state might be manipulated and skim out through electrical pulses, stated Hone. The coherence time was brief — slightly over 1 microsecond, in comparison with about 10 microseconds for a conventionally constructed coplanar capacitor, however that is solely a primary step in exploring the usage of 2D supplies on this space, he stated.
Separate work printed on arXiv in August from researchers at MIT additionally took benefit of niobium diselenide and boron nitride to construct parallel-plate capacitors for qubits. The gadgets studied by the MIT group confirmed even longer coherence instances — as much as 25 microseconds — indicating that there’s nonetheless room to additional enhance efficiency.
From right here, Hone and his group will proceed refining their fabrication methods and take a look at different kinds of 2D supplies to extend coherence instances, which replicate how lengthy the qubit is storing data. New gadget designs ought to be capable to shrink issues down even additional, stated Hone, by combining the weather right into a single van der Waals stack or by deploying 2D supplies for different components of the circuit.
“We now know that 2D supplies might maintain the important thing to creating quantum computer systems attainable,” Hone stated. “It’s nonetheless very early days, however findings like these will spur researchers worldwide to contemplate novel functions of 2D supplies. We hope to see much more work on this course going ahead.”
Supplies supplied by Columbia College Faculty of Engineering and Utilized Science. Authentic written by Ellen Neff. Be aware: Content material could also be edited for fashion and size.