Image: Photo by Professor Wolfgang Pfaff show more
Photo credit: Grainger College of Engineering at the University of Illinois Urbana-Champaign
An initiative led by Wolfgang Pfaff, an assistant professor of physics at the University of Illinois Urbana-Champaign, has a $5.8 million award from the Army Research Office, a directorate of the Army Research Laboratory of the U.S. Army Combat Capabilities Development Command Dollars received to create a new quantum computing architecture. Researchers will use fluxonium, a promising new superconducting qubit, to control and modularly connect superconducting cavities that store quantum information. A successful demonstration of inter-cavity communication through entanglement of fluxonium qubits will provide proof-of-principle for modular quantum computing.
“We are using next-generation hardware to build a modular system that, when combined, could result in a fully scalable quantum computer in the future,” Pfaff said.
Currently, the most advanced quantum devices contain hundreds of qubits, or quantum processing units, but this is still orders of magnitude insufficient for practical quantum computing. The challenge in scaling to larger systems is managing complexity and unwanted influences, both as crosstalk between qubits and interactions with the environment. Pfaff explained that modular platforms could achieve this by dividing the qubits into smaller units that are easier to control and troubleshoot. These units are controlled by additional qubits that combine through quantum entanglement to form larger, more powerful systems.
The initiative will lead to the development of a modular platform consisting of multimode cavities controlled by auxiliary fluxonium qubits. Multimode resonators made of superconducting metals have attracted attention in recent years for their ability to store quantum information in long-lived photons, and fluxonium has been predicted to have minimal impact on cavity photons, unlike other superconducting qubits. Pfaff said combining these two technologies could lead to quantum registers with unprecedented coherence times, or periods over which quantum properties are preserved.
He continued: “Right now, the best coherence times for superconducting qubits are around a millisecond. This is most likely not good enough for scalable quantum computing. By using high-coherence cavities and incorporating more advanced fluxonium qubits, we should be able to achieve at least a factor of 10 improvement in coherence time and power.”
The work will be conducted over four years at the University of Illinois, Rutgers University and the University of Texas at Austin. The final demonstration of two multimode cavities linked by entangled fluxonium qubits will take place at the University of Illinois. According to Pfaff, this will show that it is possible to combine even more units and create a truly scalable quantum computer.
Pfaff, an expert in long-distance entanglement and superconducting cavities, will work with Angela Kou, an Illinois assistant professor of physics specializing in the development of new superconducting qubit circuits; Srivatsan Chakram, a Rutgers Assistant Professor of Physics and Astronomy studying multimode cavity quantum memories; and Shyam Shankar, a Texas assistant professor of electrical and computer engineering specializing in quantum measurement techniques and remote entanglement generation.
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