1 Cold molecules Mike Tarbutt LMI Lecture, 05/11/12

What’s different about molecules?  They can vibrate  They can rotate  They are easy to polarize  Electronic excitation: vis/uv  Vibrational excitation: ir (10  m typical)  Rotational excitation: microwave (1mm – 10cm typical)

Why are people excited about cold molecules? Quantum degenerate dipolar gases Controlling biomolecules +V -V Quantum information processing e Searches for new physics e  selectron C H O H H O Cold quantum chemistry

Using molecules to measure the electron’s electric dipole moment  Electron EDM is a test of time-reversal symmetry and a search for new physics  Measurements use electrons in atoms or molecules  Experimental sensitivity proportional to degree of polarization  Molecules are much easier to polarize than atoms  Experiments on YbF (Imperial), PbO (Yale), ThO (Yale\Harvard), PbF (Oklahoma), WC (Michigan)... Nature 473, 493 (2011)

Using molecules to search for time-varying fundamental constants  Lab-based measurements – need very high precision  Astro-measurements – need sources that are far away -Faraday Discussions 142, 25 (2009) - European Physical Journal Special Topics, 163, 55 (2008) - Phys. Rev. Lett. 96, (2006) - Phys. Rev. Lett. 96, (2006)

Quantum degenerate dipolar gases Polarized molecules interact strongly with one another via dipole-dipole interactions. In a quantum degenerate gas of molecules:  Physics governed by long-range anisotropic dipole-dipole interactions  Very different to atomic case (short range van der Waals interactions)  Electric field strength tunes the interaction strength  Explore the physics of strongly-correlated quantum matter  A lattice of polar molecules can be used as a quantum simulator Repulsive Attractive

7 Quantum information processing with molecules Can use microwave photons to manipulate the rotational states of molecules. Potential for coupling polar molecules to superconducting microwave stripline resonators – hybrid quantum processors! [Nature Physics 2, 636 (2006)] [Phys. Rev. Lett. 97, (2006)] e.g. Qubits based on rotational states. Microwave pulses for single qubit rotations. Phys. Rev. Lett. 88, (2002)

Two routes to cold molecules Start with cold atoms Bind them together Start with hot molecules Cool them down To find out more: come to my CDT lectures!