Quantum Optics and Quantum Metrology section conducts experimental and theoretical research in Quantum Optics, in particular, in Quantum Information Processing and Quantum Technologies.
We use photons, from optics to microwaves interacting with a wide variety of quantum matter, such as quantum dots, single atoms, atomic ensembles and mechanical oscillators. The overarching theme is generation and manipulation of non-classical entangled states for quantum simulation, sensing and communication. The research directions span from fundamental research to device engineering. There are four experimental groups and the quantum optics theory group at the section.
Permanent faculty members
The permanent faculty members within the section are Professor Peter Lodahl , Associate professor Joerg H. Müller, Professor Eugene S. Polzik (head of the section), Professor Albert Schliesser, Professor Anders S. Sørensen, and Professor Jan W. Thomsen.
Students supervised by the section professors get involved in forefront research at all levels. We supervise approximately 15 bachelor students, 15 M.Sc. students and 20 Ph.D. students every year.
Professors of the section teach undergraduate and advanced courses, such as Optics, Quantum Mechanics, Atomic Physics, Experimental Physics, Optical Physics and Lasers, Quantum Optics I, Quantum Optics II, Quantum Nanophotonics and Quantum Information.
About the Quantum Technology
Quantum Technology is an area that is expanding massively worldwide. The section addresses most major areas within Quantum Optics: quantum simulations, communication and sensing.
The quantum optics section consists of four groups, which are among the leading groups in theirs areas worldwide.
- The Quantum Photonics group (Lodahl) specializes in solid-state quantum optics using quantum dots in photonic nanostructures to construct photonic quantum hardware. The group has demonstrated the world record of the single photon coupling into a waveguide.
- The Quantum Optomechanics group (Schliesser) specializes in quantum sensors and devices based on nano- and micromechanical resonators coupled to radio-frequency, microwave and optical fields. The group has pioneered extremely high-Q mechanical oscillators and holds the world record in quantum coherence of an opto-mechanical device at room temperature.
- The Quantum Optics Group (Polzik, Muller) has pioneered atomic ensembles as a new area within the field of quantum information. It has been developing quantum photonic interfaces between atomic ensembles and mechanical systems and has pioneered measurements not limited by the Heisenberg uncertainty bound.
- The Quantum Metrology (Thomsen) develops new approaches to atom clocks based on cold atoms.
- The Theoretical Quantum Optics group (Sørensen) is a leading group in the physical implementation of quantum information processing using atoms, ions, optomechanics and solid-state systems. Recently the group made a major contribution to exploiting dissipation to produce entanglement and perform quantum information processing.
External grants funding research
The section PIs attract a large number of external grants funding their research. In 2012-2018 the group PIs were awarded 5 ERC grants (Polzik – two ERC Advanced Grants, Lodahl - ERC Advanced grant; Sørensen - ERC Consolidator grant, Schliesser – ERC Starting Grant) which are widely recognized as the stamps of top quality research. In 2017 three group members (Lodahl – PI, Schliesser and Sørensen co-PIs) were awarded the Center of Excellence Grant from the Danish National Research Foundation, a 10 year exclusive funding awarded in a strong competition across all sciences and humanities in Denmark.
The section members are very active in the European Flagship program in Quantum Technologies with three grants awarded within the first Flagship call. Eugene Polzik is the National Quantum Node for Denmark for the Flagship Coordination Action.
Nano-opto-electro-mechanical systems, L. Midolo, A. Schliesser, A. Fiore, Nature Nanotechnology 13, 11 (2018). A new class of nano-devices is developed for applications in telecommunication, metrology, medical imaging and quantum computation.
Lodahl, S. Mahmoodian, S. Stobbe, A. Rauschenbeutel, P. Schneeweiss, J. Volz, H. Pichler, and P. Zoller, Chiral Quantum Optics, Nature 541, 473 (2017). We show that photon-emitter interaction can be directional in photonic waveguides, which opens new perspectives for quantum optics and quantum information processing.
Quantum back action evading measurement of motion in a negative mass reference frame. C. B. Møller, R. A. Thomas, G. Vasilakis, E. Zeuthen, Y. Tsaturyan, K. Jensen, A. Schliesser, K. Hammerer, and E. S. Polzik. Nature, 547, 191 (2017). First experimental step towards measurement of motion not limited by the Heisenberg uncertainty bound.
Ultracoherent nanomechanical resonators via soft clamping and dissipation dilution, Y. Tsaturyan, A. Barg, E. S. Polzik, A. Schliesser, Nature Nanotechnology 12, 776 (2017). We introduce and demonstrate a novel method to realise nanomechanical resonators with unprecedented coherence—Q-factors enabling a new class of experiments.
Generation of a squeezed state of an oscillator by stroboscopic back-action-evading measurement. G. Vasilakis, H. Shen, K. Jensen, M. Balabas, D. Salart, B. Chen, and E. S. Polzik. Nature Physics, doi:10.1038/nphys3280 (2015). First demonstration of a squeezed state of macroscopic material oscillator.
Single-photon non-linear optics with a quantum dot in a waveguide, A. Javadi, I. Sollner, M. Arcari, S.L. Hansen, L. Midolo, S. Mahmoodian, G. Kirsanske, T. Pregnolato, E. H. Lee, J. D. Song, S. Stobbe, and P. Lodahl, Nature Communications 6, 8655 (2015). We show that a single quantum dot efficiently coupled to a waveguide can serve as a highly-efficient single-photon nonlinearity opening new prospects for quantum gates based on photons.
Near-unity coupling efficiency of a quantum emitter to a photonic-crystal waveguide, M. Arcari, I. Sollner, A. Javadi, S. Lindskov Hansen, S. Mahmoodian, J. Liu, H. Thyrrestrup, E.H. Lee, J.D. Song, S. Stobbe, and P. Lodahl, Physical Review Letters 113, 093603 (2014). We show a single-photon source based on a quantum dot in a photonic-crystal waveguide with a record-high internal efficiency exceeding 98%.
Dissipative production of a maximally entangled steady state of two quantum bits, Y. Lin, J. P. Gaebler, F. Reiter, T. R. Tan, R. Bowler, A. S. Sørensen, D. Leibfried and D. J. Wineland, Nature 504, 415 (2013). We demonstrated for the first time that dissipation could be used to produce a maximally entangled state of two qubits.
Optical detection of radio waves through a nanomechanical transducer, T. Bagci, A. Simonsen, S. Schmid, L. G. Villanueva, E. Zeuthen, J. Appel, J. M. Taylor, A. Sørensen, K. Usami, A. Schliesser & E. S. Polzik, Nature 507, 81 (2014). The first step towards quantum limited connection between low frequency signals optical fields opening new possibilities from signal detection to quantum communication. A patent application for the method has been filed.
Near-Heisenberg-Limited Atomic Clocks in the Presence of Decoherence, J. Borregaard and A. S. Sørensen, Phys. Rev. Lett. 111, 090801 (2013). Using entanglement to improve atomic clocks is a major goal in quantum information. We showed that with a suitable measurement procedure it is possible to get full advantage despite the decoherence.
Deterministic quantum teleportation between distant atomic objects. H. Krauter, D. Salart, C. A. Muschik, J. M. Petersen, Heng Shen, T. Fernholz, and E. S. Polzik. Nature Phys., 9, 400 (2013). Cover page story. First demonstration of quantum teleportation between macroscopic material objects.