Nav: Home

Further improvement of qubit lifetime for quantum computers

December 08, 2016

Jülich, 8 December 2016. An international team of scientists has succeeded in making further improvements to the lifetime of superconducting quantum circuits. An important prerequisite for the realization of high-performance quantum computers is that the stored data should remain intact for as long as possible. The researchers, including Jülich physicist Dr. Gianluigi Catelani, have developed and tested a technique that removes unpaired electrons from the circuits. These are known to shorten the qubit lifetime (to be published online by the journal Science today, DOI: 10.1126/science.aah5844).

Quantum computers could one day achieve significantly higher computing speeds than conventional digital computers in performing certain types of tasks. Superconducting circuits belong to the most promising candidates for implementing quantum bits, known as qubits, with which quantum computers can store and process information. The high error rates associated with previously available qubits have up to now limited the size and efficiency of quantum computers. Dr. Gianluigi Catelani of the Peter Grünberg Institute (PGI-2) in Jülich, together with his colleagues has now found a way to prolong the time in which the superconducting circuits are able to store a "0" or a "1" without errors. Beside Catelani, the team comprises researchers working in the USA (Massachusetts Institute of Technology, Lincoln Laboratory, and the University of California, Berkeley), Japan (RIKEN), and Sweden (Chalmers University of Technology).

When superconducting materials are cooled below a material-specific critical temperature, electrons come together to form pairs; then current can flow without resistance. However, so far it has not been possible to build superconducting circuits in which all electrons bundle together. Single electrons remain unpaired and are unable to flow without resistance. Due to these so-called quasiparticles, energy is lost and this limits the length of time that the circuits can store data.

Researchers have now developed and tested a technique that can temporarily remove unpaired electrons away from the circuit; with the help of microwave pulses, they are in effect "pumped out". This results in a three-fold improvement in the lifespan of the qubits.

"The technique can in principle be put to immediate use for all superconducting qubits", explained Catelani, who, as a theoretical physicist has contributed to the analysis and interpretation of the experimental data. However, he emphasised that the lifespan of qubits is only one of many hurdles in the development of complex quantum computers. Moreover, the new technique means that the quasiparticles are not permanently removed, but flow back again and again. The scientists have another solution ready to solve this problem: the pumping technique can be combined with another method that permanently traps the quasiparticles. Catelani, together with his colleagues from Jülich and Yale, has already analysed and tested such a quasiparticle "trap". Their results were published in September in the journal Physical Review B (DOI: 10.1103/PhysRevB.94.104516).
Original publication:

Suppressing relaxation in superconducting qubits by quasiparticle pumping;
Simon Gustavsson et al.;
Science (to be published online on 8. Dec. 2016), DOI: 10.1126/science.aah5844 (available from 8:00 pm CET).


Illustration of the filtering of unwanted quasiparticles (red spheres) from a stream of superconducting electron pairs (blue spheres) using a microwave-driven pump.
Copyright: Philip Krantz, Krantz NanoArt

Further information:

Forschungszentrum Jülich:

Research at the Peter Grünberg Institute, Theoretical Nanoelectronics (PGI-2):

Press release from 17.4.2014 "Quantum computing: 50-year-old prediction confirmed":


Dr. Gianluigi Catelani,
Peter Grünberg Institute, Theoretical Nanoelectronics (PGI-2),
Forschungszentrum Jülich, Germany
Phone: +49 2461 61-9360

Press contact:

Angela Wenzik, Science Journalist,
Forschungszentrum Jülich, Germany
Phone: +49 2461 61-6048,

Forschungszentrum Juelich

Related Quantum Computers Articles:

Study takes step toward mass-producible quantum computers
Study takes step toward mass-producible quantum computers.
Testing quantum field theory in a quantum simulator
Quantum field theories are often hard to verify in experiments.
Refrigerator for quantum computers discovered
Researchers at Aalto University have invented a quantum-circuit refrigerator, which can reduce errors in quantum computing.
New quantum liquid crystals may play role in future of computers
First 3-D quantum liquid crystals may have applications in quantum computing.
'Virtual' interferometers may overcome scale issues for optical quantum computers
A team of researchers from RMIT, the University of Sydney and UTS have devised an entirely new way of implementing large-scale interferometers that will dramatically miniaturize optical processing circuitry.
Further improvement of qubit lifetime for quantum computers
An international team of scientists has succeeded in making further improvements to the lifetime of superconducting quantum circuits.
Construction of practical quantum computers radically simplified
Scientists at the University of Sussex have invented a ground-breaking new method that puts the construction of large-scale quantum computers within reach of current technology.
New quantum states for better quantum memories
How can quantum information be stored as long as possible?
A new class of materials could realize quantum computers
Scientists at EPFL and PSI have discovered a new class of materials that can prove ideal for the implementation of spintronics.
New 3-D wiring technique brings scalable quantum computers closer to reality
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

Related Quantum Computers Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...