New method prevents quantum computers from crashing

September 09, 2020

Qubits--the carriers of quantum information--are prone to errors induced by undesired environmental interactions. These errors accumulate during a quantum computation and correcting them is thus a key requirement for a reliable use of quantum computers.

It is by now well known that quantum computers can withstand a certain amount of computational errors, such as bit flip or phase flip errors. However, in addition to computational errors, qubits might get lost altogether. Depending on the type of quantum computer, this can be due to actual loss of particles, such as atoms or ions, or due to quantum particles transitioning for instance to unwanted energy states, so that they are no longer recognized as a qubit. When a qubit gets lost, the information in the remaining qubits becomes scrambled and unprotected, rendering this process a potentially fatal type of error.

Detect and correct loss in real time

A team of physicists led by Rainer Blatt from the Department of Experimental Physics at the University of Innsbruck, in collaboration with theoretical physicists from Germany and Italy, has now developed and implemented advanced techniques that allow their trapped-ion quantum computer to adapt in real-time to loss of qubits and to maintain protection of the fragile stored quantum information. "In our trapped-ion quantum computer, ions hosting the qubits can be trapped for very long times, even days", says Innsbruck physicist Roman Stricker. "However, our ions are much more complex than a simplified description as a two-level qubit captures. This offers great potential and additional flexibility in controlling our quantum computer, but unfortunately it also provides a possibility for quantum information to leak out of the qubit space due to imperfect operations or radiative decay." Using an approach developed by the Markus Müller's theoretical quantum technology group at RWTH Aachen University and Forschungszentrum Jülich, in collaboration with Davide Vodola from the University of Bologna, the Innsbruck team has demonstrated that such leakage can be detected and corrected in real-time. Müller emphasizes that "combining quantum error correction with correction of qubit loss and leakage is a necessary next step towards large-scale and robust quantum computing."

Widely applicable techniques

The researchers had to develop two key techniques to protect their quantum computer from the loss of qubits. The first challenge was to detect the loss of a qubit in the first place: "Measuring the qubit directly was not an option as this would destroy the quantum information that is stored in it", explains Philipp Schindler from the University of Innsbruck. "We managed to overcome this problem by developing a technique where we used an additional ion to probe whether the qubit in question was still there or not, without disturbing it", explains Martin Ringbauer. The second challenge was to adapt the rest of the computation in real-time in case the qubit was indeed lost. This adaptation is crucial to unscramble the quantum information after a loss and maintain protection of the remaining qubits. Thomas Monz, who lead the Innsbruck team, emphasizes that "all the building blocks developed in this work are readily applicable to other quantum computer architectures and other leading quantum error correction protocols."
The research was financed by the Austrian Science Fund FWF, the Austrian Research Promotion Agency FFG and the European Union, among others.

University of Innsbruck

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to