Christine Muschik and J. Ignacio Cirac

1. Entanglement generated by Dissipation Christine Muschik and J. Ignacio Cirac Max-Planck-Institut für Quantenoptik Hanna Krauter, Kasper Jensen, Jonas Meyer Petersen and Eugene Polzik Niels Bohr Institute, Danish Research Foundation Center for Quantum Optics (QUANTOP)

2. Entanglement

3. Entanglement

4. Steady State Entanglement

6. Basic ingredient in most applications in the field of quantum information But: Lifetimes are usually very short Therefore: Need for much longer lifetimes! Motivation: Quantum entanglement

7. Basic ingredient in most applications in the field of quantum information But: Lifetimes are usually very short Therefore: Need for much longer lifetimes! Motivation: Quantum entanglement Typically: Quantum states are fragile under decoherence

8. Basic ingredient in most applications in the field of quantum information But: Lifetimes are usually very short Therefore: Need for much longer lifetimes! Motivation: Quantum entanglement Typically: Quantum states are fragile under decoherence Avoidance of dissipation by decoupling the system from the environment

9. Basic ingredient in most applications in the field of quantum information But: Lifetimes are usually very short Therefore: Need for much longer lifetimes! Quantum states are fragile under decoherence Avoidance of dissipation by decoupling the system from the environment Strict isolation! Motivation: Quantum entanglement Typically:

10. Motivation:

11. Motivation:

12. Motivation: New approaches Use the interaction of the system with the environment

13. Motivation: New approaches Use the interaction of the system with the environment Dissipation drives the system into the desired state

14. Use the interaction of the system with the environment Dissipation drives the system into the desired state Robust method to create extremely long-lived and robust entanglement Motivation: New approaches

15. Motivation: Procedure:

16. Motivation: Procedure: Engineer the coupling

17. Motivation: Procedure: Engineer the coupling Steady state = desired state

18. Motivation: Procedure: Engineer the coupling Steady state = desired state Arbitrary initial state

19. Motivation: Procedure: Engineer the coupling Steady state = desired state Arbitrary initial state

20. Proposals: Single trapped ion J. F. Poyatos, J. I. Cirac and P. Zoller, Phys. Rev. Lett. 77,4728 (1996) Atoms in two cavities B. Kraus and J. I. Cirac, Phys. Rev. Lett. 92, 013602 (2004) Many-body systems S. Diehl, A. Micheli, A. Kantian, B. Kraus, H.P. Büchler, P. Zoller, Nature Physics 4, 878 (2008) F. Verstraete, M.M. Wolf, J.I. Cirac, Nature Physics 5, 633 (2009) Quantum phase transitions State preparation Quantum computing Motivation: Procedure: Engineer the coupling Steady state = desired state Arbitrary initial state

21. Motivation: Procedure: Engineer the coupling Steady state = desired state Arbitrary initial state

22. Setup:

23. Main idea: Hamiltonian:

24. Main idea: Hamiltonian: Master equation:

25. Main idea: Hamiltonian: Master equation: Unique Steady State:

26. magnetic fields laser Setup:

27. magnetic fields laser Reservoir: common modes of the electromagnetic field. Control: Laser and magnetic fields Setup:

28. Setup: laser

29. laser Setup:

30. laser Setup:

31. laser Setup:

32. laser Setup:

33. Theory: Masterequation: +undesired processes Entanglement:

34. Theory: Entanglement: ideal case

35. Theory: Entanglement: ideal case Entanglement: including undesired processes : noise rate : polarization

36. Theory: Two-level model Experiment: Multi-level structure Experimental realization of purely dissipation based entanglement:

37. Theory: Two-level model Experiment: Multi-level structure (nuclear spin I=7/2) Experimental realization of purely dissipation based entanglement:

38. Experimental results:

39. Experimental results: EPR variance

40. Experimental results: Longitudinal spin EPR variance

41. Experimental results:

42. Conclusions and Outlook: First observation of entanglement generated by dissipation

43. Conclusions and Outlook: First observation of entanglement generated by dissipation Entanglement was produced with macroscopic atomic ensembles, and lasted much longer than in previous experiments where entanglement was generated using standard methods.

44. Conclusions and Outlook: First observation of entanglement generated by dissipation Entanglement was produced with macroscopic atomic ensembles, and lasted much longer than in previous experiments where entanglement was generated using standard methods. This work paves the way towards the creation of long lived entanglement, potentially lasting for several minutes or longer.

45. Atoms with two-level atomic ground states, e.g. Yb 171 Conclusions and Outlook: Realization of Steady State Entanglement:

46. Atoms with two-level atomic ground states, e.g. Yb 171 Conclusions and Outlook: Realization of Steady State Entanglement: Increased optical depth + optical pumping

47. Atoms with two-level atomic ground states, e.g. Yb 171 Conclusions and Outlook: Realization of Steady State Entanglement: Increased optical depth + optical pumping Reduced spin-flip collisions Better coatings, lower temperatures

48. Summary: Proposal for long-lived entanglement Dissipatively driven entanglement General theoretical model for quadratic Hamiltonians Future Other systems, e.g. optomechanical oscillators

49. Steady state: Main idea: Steady state:

50. Effective ground state Hamiltonian: Master equation: Entanglement: