New circulator uses mechanics

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Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Mathematically they require breaking of time-reversal symmetry, typically achieved using magnetic materials and more recently using the quantum Hall effect, parametric permittivity modulation or Josephson nonlinearities. We realized an in-situ reconfigurable, magnetic-free, on-chip circulator based on reservoir-engineered electromechanic interactions.

You can find our most recent result here: Nature Communications, reprintSI.

Frontiers of Circuit QED and Optomechanics

In February we are organizing a conference in Semmering, a small skiing resort close to Vienna. The topics include quantum opto- and electromechanics, circuit QED and everything in between. More details including our current list of invited speakers at


[Update: Due to a delay in the construction and renovation works at Hotel Panhans we were forced to relocate the conference to the IST Austria campus.]

ERC Grant

LOGO-ERCWe got an ERC starting grant to work on QUNNECT: A Fiber Optic Transceiver for Superconducting Qubits.

Many researchers are convinced that superconducting quantum processors will soon help solve complex problems faster, improve optimization and simulation, and boost the progress in artificial intelligence. A worldwide quantum web is the next logical step. It would not only improve communication security, it represents the key to unlock the full potential of the new quantum-computing paradigm.

Unfortunately, research in optical quantum networks and superconducting devices has progressed largely independently so far. While superconducting qubits are ideally suited for on-chip integration and fast processing, they are problematic for quantum communication. Only just now we have gained sufficient insight into low loss materials, the required fabrication technology, and the precision measurement techniques necessary to bridge the two worlds.

We will integrate silicon photonics for low-loss fiber optic communication with superconducting circuits for quantum processing on a single microchip. As intermediary transducer we will focus on two approaches: (1) quantum ground state cooled nanoscale mechanical and (2) low-loss electro-optic nonlinear circuit elements. One novelty of our approach is the tight on-chip integration which will be the key for realizing a low-loss and high-bandwidth transceiver, for preparing remote entanglement of superconducting qubits, and for extending the range of current fiber optic quantum networks.


New Phase Transition Observed

screen-shot-2017-02-01-at-12-47-21Phase transitions, such as the change of liquid water into ice, help elucidate the complex behavior of systems composed of many particles and occur in all areas of physics. Recently, theorists have predicted that a cavity containing only a single atom should transition from opaque to transparent when the input photon flux reaches a critical number. And just as water and ice can coexist at the melting point temperature, the cavity was predicted to be both opaque and transparent close to the critical point, stochastically switching between the two states. This coexistence is a hallmark for a so-called first-order phase transition, which has been observed for the first time in a dissipative quantum system.

The article in Physical Review X and the IST press release as well as some news coverage on  DerStandard.