New thermometer improves quantum computer stability

Scientists from Aalto University, Université Grenoble Alpes, and the University of Konstanz have developed a reliable way to measure heat dissipation in superconducting circuits. This could lead to more stable and higher fidelity quantum machines, writes Aalto University in a press release.

The Need for Better Heat Detection

Heat dissipation is a crucial element in the development of quantum devices such as computers. As heat sets limits for traditional computing, so it does for quantum computers. Therefore, detecting and controlling the heat dissipation of quantum computers is central to developing better and more stable machines.

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Jukka Pekola’s Team

Beginning in 2018, Professor Jukka Pekola and doctoral researcher Bayan Karimi of Aalto University have been developing a new kind of thermometer for measuring tiny energy changes. As part of the Marie Curie Network, which enables researchers to collaborate across borders, Pekola and Karimi, along with Senior Scientist Joonas Peltonen, went to Grenoble in France to share the tools they developed at Aalto with French researchers.

Detecting Heat Dissipation in a Phase Slip

The scientists in Grenoble, led by Dr. Clemens Winkelmann, put the theoretical models and experimental setups to work and used them to detect the heat dissipation of a phase slip in a Josephson junction. A Josephson junction is a key part of a superconducting circuit in which two superconductors produce an always-on current between them without any voltage. A phase slip, in turn, refers to how quantum particles change their status over time, which produces an incredibly tiny but crucial amount of heat when it happens.

With Karimi’s and Pekola’s tools, Winkelmann and the team at Grenoble, particularly the doctoral student Efe Gümüs, observed a phase slip in a Josephson junction and were able, for the first time, to measure the instantaneous heat production caused by the slip. The group at Konstanz, led by Professor Wolfgang Belzig, provided the theoretical models of the experiment.

Future with quantum computers also calls for encryption of older data

Since it will not be very long before quantum computers are commonplace, people are already working hard on the security for this new situation.

Improving Quantum Devices

The experiment represents the first time that these quantum thermodynamical ideas were realized in practice. With better detection and control of heat dissipation, the discovery also has the potential to lead to more stable and higher fidelity quantum computers.

Pekola says that the work at Aalto focuses on getting to the heart of heat in quantum devices. ‘We want to go to the tiniest detail of thermodynamics – to the level of single excitations. We want to examine quantum circuits and see how they release energy into their environment. The result can eventually be a tool for opening an entirely new perspective on quantum thermodynamics. Experimental results like these represent great strides forward in our understanding of thermodynamics in the quantum world.’