Physicists from Aalto University and an international team have made a groundbreaking discovery that could revolutionize the future of quantum computing. By tracing the coherence decay of superconducting qubits to thermal dissipation, they have shed new light on one of the most pressing challenges in the field.
Unraveling the Mystery of Qubit Decay
Physicists have long puzzled over how and where superconducting qubits, the building blocks of advanced quantum computers or ultrasensitive detectors, lose heat.
But now, a team of researchers at Aalto University led by their Spanish colleagues have found a solution. In this way, by validating the prediction of qubit coherence loss without tomographically detectingthe quantum state as thermal dissipation in the electrical circuit holding the qubit, they have successfully broken a new ground in our understanding for quantum systems.
This finding is especially important because qubits with longer coherence times (meaning they are less likely to decay) can perform more operations and thus execute more complex calculations than what classical computing environments can handle. Now that the origin of this decay has been traced, researchers can eventually develop even more effective and reliable qubits; one step closer to where quantum computing might finally start matching lofty expectations.
The Quantum Leap: Measuring Thermal Dissipation
The groundbreaking aspect of the team’s work was their innovative measurement technique to map the thermal dissipation in a single Josephson junction —the building block qubit.
Rather than dealing with these large arrays of Josephson junctions, which can cause over-complex behavior and instabilities and the researchers reduced their experiments to a single junction. For each phase transition, they placed an ultra-sensitive thermal absorber at the same junction and passively measured the weak radiation that is emitted for the dielectric mode on a broad frequency range up to 100 gigahertz.
The clever setup enabled them to follow that elusive source of the energy loss for the first time, as detailed in a previous report. This, the researchers said, would be similar to a person at the beach being warmed by a campfire without actually raising the temperature of the ambient air around them.
What the team found is that the culprit behind qubits’ dissipation was still this same type of radiation — a major discovery in understanding qubit decay. This changes the way we think quantum computers could be like and provides a new degree of freedom for devices with more robust and efficient quantum systems, capturing building blocks for the next generation of quantum computing and quantum sensing technology.
Conclusion
By Andreas Heinonen / AaltoUniversityThe international team, that includes a group from Aalto University headed by Professor Pekola, has opened up an important new area of application for quantum thermodynamics. By demonstrating that the primary source of coherence decay in some superconducting qubits is the same process as thermal dissipation, they have shown a new route for improving quantum systems with applications across quantum information sciences and ultrasensitive detectors. The discovery marks a major advance in our understanding of this exotic form of matter, its implications for the fundamental physics behind these emerging technologies will also likely lead to a deep reshaping of efforts in the field going forward.
