- Mechanical systems in the quantum regime
Our research involves theoretical studies of optomechanical or electromechanical setups with a focus on controlling micromechanical oscillators in the quantum regime, motivated in part by applications such as accurate sensing or quantum signal processing. We are also interested in the interplay of mechanical and transport properties in low-dimensional materials, e.g., graphene or topological materials.
- Macroscopic nonclassicality
We are interested in nonclassicality witnesses, in particular for revealing quantum behaviour of systems excited to large numbers of quanta, i.e., high-intensity electromagnetic fields, or of mechanical degrees of freedom at the mesoscopic or macroscopic mass scale. This is motivated both by realization of robust quantum applications as well as fundamental issues, such as alternative theories of decoherence or the relation between quantum mechanics and gravity.
- Foundations of quantum mechanics
Much of our research in this area is centred around quantum measurements: weak measurements, sequential measurements, symmetry-constraints, incompatibility. Other interests include the quantum-classical transition, quantum reference frames, contextuality, and general probabilistic theories.
Please feel free to contact us if you are interested in our research.
At the moment, we do not have open PhD or postdoc positions.
We may be able to welcome exchange students who wish to write their Master thesis with us. Please get in touch if this is of interest to you.
Our group has received funding through QuantERA - a European Research Area Network (ERA-NET) Cofund Programme in the field of Quantum Technologies. USN participates in two QuantERA projects: QuaSeRT (Optomechanical quantum sensors at room temperature, 2018-2021) and MQSens (Quantum sensing with nonclassical mechanical oscillators, 2022-2025).
Networks and collaborations
We are participating in the following COST Actions:
Quantum technologies in space is a COST Action which will identify fundamental questions in quantum mechanics that may be answered through experiments in space. The project will identify possible applications of quantum technology in space, and includes technology development in cooperation with national space agencies and industrial partners.
In recent years, ion traps have developed from a topic of fundamental research into a versatile tool for a wide range of research topics and quantum technologies. The aim of this COST Action is to enhance the current applications of trapped ions by supporting Europe-wide collaborations and knowledge exchange, and to allow these technologies to be taken a step further towards their commercialisation.
Two-dimensional quantum motion of a levitated nanosphere
A. Ranfagni, K. Børkje, F. Marino, F. Marin, Phys. Rev. Research 4, 033051 (2022)
Incompatibility of effects in general probabilistic models
R. Beneduci. L. Loveridge, J. Phys. A: Math. Theor. 55 254005 (2022)
Nonclassical photon statistics in two-tone continuously driven optomechanics
K. Børkje, F. Massel, J.G.E. Harris, Phys. Rev. A 104, 063507 (2021)
A quantum reference frame size-accuracy trade-off for quantum channels
T. Miyadera, L. Loveridge, J. Phys.: Conf. Ser. 1638 012008 (2020)
A relational perspective on the Wigner-Araki-Yanase theorem
L. Loveridge, J. Phys.: Conf. Ser. 1638 012009 (2020)
Backaction-evading measurement of entanglement in optomechanics
F. Massel, Phys. Rev. A 100, 023824 (2019)
Heterodyne photodetection measurements on cavity optomechanical systems: Interpretation of sideband asymmetry and limits to a classical explanation,
K. Børkje, Phys. Rev. A 94, 043816 (2016)
Position Measurements Obeying Momentum Conservation,
P. Busch and L. Loveridge, Phys. Rev. Lett. 106, 110406 (2011)
Quantum theory of successive projective measurements,
L. M. Johansen, Phys. Rev. A 76, 012119 (2007)
A. Nunnenkamp, K. Børkje, S.M. Girvin, Phys. Rev. Lett. 107, 063602 (2011)
Stabilized entanglement of massive mechanical oscillators,
C. F. Ockeloen-Korppi, E. Damskägg, J. M. Pirkkalainen, M. Asjad, A. A. Clerk, F. Massel, M. J. Woolley, M. A. Sillanpää, Nature 556, 478 (2018)
Symmetry, Reference Frames and Relational Quantities in Quantum Mechanics,
L. Loveridge, T. Miyadera and P. Busch. Found. Phys. 48, 2 (2018)
Weak measurements with arbitrary probe states,
L. M. Johansen, Phys. Rev. Lett. 93, 120402 (2004)