Quantum mechanics is at the heart of our technology and economy - the laser and the transistor are quantum devices - but its full potential is far from being realized. Recent technological advances in optics, nanoscience and engineering allow experimentalists to create artificial structures or put microscopic and mesoscopic systems under new manipulable conditions in which quantum phenomena play a fundamental role.

Quantum technologies exploit these effects with practical purposes. The objective of Quantum Science is to discover, study, and control quantum efects at a fundamental level. These are two sides of a virtuous circle: new technologies lead to the discovery and study of new phenomena that will lead to new technologies.

Our group's aim is  to control and understand quantum phenomena in a multidisciplinary intersection of  Quantum Information, Quantum optics and cold atoms, Quantum Control, Spintronics, Quantum metrology, Atom interferometry, Superconducting qubits and Circuit QED and Foundations of Quantum Mechanics.



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Carsten Klempt (University of Hannover, Germany) ( Seminar)


  • Start: 03/10/2016


Talk by Carsten Klempt (University of Hannover, Germany)
Title: Spin dynamics as a source of nonclassical states of matter
Place: Salon de Grados
Time: 12:00–13:00, Thursday, 10 March 2015


Spin dynamics in Bose-Einstein condensates allows for the
generation of many-particle entangled states. We will show that it can be used to create a two-mode squeezed vacuum state. If the total number of particles in the squeezed vacuum state is measured, the state can be treated as a mixture of Dicke states. These Dicke states with up to 8000 atoms are useful for interferometry [1] beyond the shot noise limit. The states contain at least genuine 28-particle entanglement [2]. Additionally, we infer a generalized squeezing parameter of −11.4(5) dB.     The state is also analyzed by atomic homodyne detection, revealing coherences between the Dicke states. The homodyning allows for a measurement of the phase and amplitude quadratures which exhibit strong correlations –  fulfilling Reid`s criterion for Einstein-Podolsky-Rosen  entanglement [3]. In addition, a full reconstruction of the  underlying quantum state is obtained from a Maximum- Likelihood analysis. Finally, we employ the created state to demonstrate a proof-of-principle operation of an atomic clock  beyond the standard quantum limit. In our protocol, an empty mode is replaced by squeezed vacuum, realizing Caves squeezing with neutral atoms for the first time.

[1] B. Lücke, M. Scherer, J. Kruse, L. Pezz., F. Deuretzbacher, P.
Hyllus, O. Topic, J. Peise, W. Ertmer, J. Arlt, L. Santos, A. Smerzi,
C. Klempt, Twin matter waves for interferometry beyond the classical limit, Science 334, 773 (2011).

[2] B. Lücke, J. Peise, G. Vitagliano, J. Arlt, L. Santos, G. Toth,
C. Klempt, Detecting Multiparticle Entanglement of Dicke States, Phys. Rev. Lett. 112, 155304 (2014).

[3] J. Peise, I. Kruse, K. Lange, B. Lücke, L. Pezz., J. Arlt, W.
Ertmer, K. Hammerer, L. Santos, A. Smerzi, C. Klempt, Satisfying the Einstein–Podolsky–Rosen criterion with massive particles, Nat. Commun. 6, 8984 (2015).