Illustration of a quantum system (silver arrow and yellow, green and purple orbitals) interacting with a resonator (two mirrors and pink light field between them). In addition, the quantum system is controlled by a control field (green laser). A photon (pink luminous drop) has been emitted into an optical fibre through one of the mirrors. Copyright: Benedikt Tissot

Making quantum bits fly

We have developed a method that could enable the stable exchange of information in quantum computers. In the leading role: photons that make quantum bits "fly".

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An artist's impression of electron spin qubits inside semiconductor quantum dots.

Research focus

Our research is focused on quantum computing, spin physics and spin qubits, hybrid quantum systems, 2D materials, time-domain quantum optics.

The figure shows an artist's impression of electron spin qubits inside semiconductor quantum dots.

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Current news



Artistic impression of spin-based semiconductor quantum processor.

Review on spin qubits

G. Burkard, T. D. Ladd, A. Pan, J. M. Nichol, and J. R. Petta, Rev. Mod. Phys. 95, 025003 (2023).

Spin qubits, employing the fundamental quantum property of intrinsic angular momentum of individual electrons and nuclei, continue to develop and evolve. This review summarizes progress in four current qubit types: single spin qubits, donor spin qubits, singlet triplet spin qubits, and exchange-only spin qubits. 

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The temporal fluctuator model to describe temporally correlated errors.

Ability of error correlations to improve the performance of variational quantum algorithms

J. Kattemölle and G. Burkard
Phys. Rev. A 107, 042426 (2023)

Selected as Editor's Suggestion.

The quantum approximate optimization algorithm (QAOA) has the potential of providing a useful quantum advantage on noisy intermediate-scale quantum (NISQ) devices. The effects of uncorrelated noise on variational quantum algorithms such as QAOA have been studied intensively. Recent experimental results, however, show that the errors impacting NISQ devices are significantly correlated. We introduce a…

A two-level system (gubit, shown in blue) with energy splitting ωq is affected by noise δωq (red) and is placed inside a single-mode electromagnetic cavity with frequency ωc. Partially transparent mirrors allow for the interaction of the qubit-cavity system with external modes. An input field binðtÞ enters at port 1, causing an output field boutðtÞ that leaves the cavity at port 2, thereby creating a time-dependent transmission through the system from left to right.

Fingerprints of Qubit Noise in Transient Cavity Transmission

P. M. Mutter, G. Burkard
Phys. Rev. Lett. 128, 236801 (2022)

Noise affects the coherence of qubits and thereby places a bound on the performance of quantum computers. We theoretically study a generic two-level system with fluctuating control parameters in a photonic cavity and find that basic features of the noise spectral density are imprinted in the transient transmission through the cavity. We obtain analytical expressions for generic noise and proceed to study the cases of quasistatic,…

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