# Two articles from ITP in first issue ever of QST journal

We are proud that our group has two articles in the first issue ever of the new journal ‘Quantum Science and Technology’:

**Coherent control of quantum systems as a resource theory**

J.M. Matera, D. Egloff, N. Killoran, and M.B. Plenio

Quantum Sci. Technol. **1**, 01LT01 (2016)|ArXiv

While controlling a quantum system is a standard task nowadays, we are still far away from developing quantum computers, and one might wonder what is the difference between the two. Qualitatively the difference is that for quantum computing one needs to control quantum systems in a quantum way, using quantum systems instead of directly using the large apparata or (classical) electromagnetical fields that often are enough to control a quantum system directly. In this letter we make this idea precise by building a theory which allows us to quantify the usefulness of controlling a quantum system through a quantum system instead of using a classical one.

**Realising a quantum absorption refrigerator with an atom-cavity system**

M. Mitchison, M. Huber, J. Prior, M.P. Woods and M.B. Plenio

Quantum Sci. Technol. **1**, 015001 (2016)|ArXiv

licensed under CC BY 3.0

Cooling of atomic motion is an essential precursor for many interesting experiments and technologies, such as quantum computing and simulation using trapped atoms and ions. In most cases, this cooling is performed using lasers to create a kind of light-induced friction force which slows the atoms down. This process is often rather wasteful, because lasers use up a huge amount of energy relative to the tiny size of the atoms we want to cool. Here, we propose to solve this problem using a quantum absorption refrigerator: a machine that is powered only by readily available thermal energy, such as sunlight, as it flows through the device. We describe how to build such a refrigerator, and predict that sunlight could actually be used to cool an atom to nearly absolute zero temperature. The refrigerator works by trapping the sunlight between two mirrors, in such a way that every single photon makes a significant contribution to the friction force slowing the atom down. Similar schemes could eventually be important for reducing the energy cost of cooling in future quantum technologies.

# News

Julen Pedernales did it again, Best Post Prize at the UniKORN Poster Session 2021

Martin Plenio is listed as highly cited researcher for the fourth time in a row.

Our work on Quantum Physics and Biology featured Local and National Radio

Ludovico Lami wins a Humboldt Fellowship to continue his work in our group for another 2 years

# Most Recent Papers

**Efficient construction of matrix-product representations of many-body Gaussian states***, *Phys. Rev. A 104, 012415 (2021)

**One-shot manipulation of entanglement for quantum channels***, *IEEE Trans. Inf. Theo. 67, 5339 (2021)

**Enhanced force sensitivity and entanglement in periodically driven optomechanics**, Phys. Rev. A 103, L061501 (2021)

# Contact

Ulm University

Institute of Theoretical Physics

Albert-Einstein-Allee 11

D - 89069 Ulm

Germany

Tel: ++49 / 731 / 50 - 22911

Fax: ++49 / 731 / 50 - 22924

Office: Building M26, room 4117

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