An atomic seesaw

Valerie Jamieson

Sunayana Dutta, B. Chatterjee, Pankaj Kumar Mishra +3 more

Abstract We study the tunneling dynamics of N = 10 one-dimensional interacting bosons confined in a temporally driven double well potential that imitates a quantum seesaw and how we can manipulate these dynamics by changing the drive of the seesaw potential. We emulate the seesaw with a driven double well potential and consider two driving protocols: an harmonic constant-frequency drive and a chirped drive with linearly increasing frequency. We consider the time-dependent many-body Schrödinger equation of a repulsively interacting quasi-one-dimensional few-boson system. We solve it by using the multiconfigurational time-dependent Hartree method for bosons (MCTDHB) as implemented in the MCTDH-X software. For an harmonic drive and at small values of the driving amplitude, the dynamics of the particles become very slow rendering a stationary-like state. In a phase-space picture the population imbalance between the wells follows a trajectory which is restricted to a comparatively small region of space. For an harmonic drive at intermediate amplitudes, the dynamics become periodic in nature, implying that the bosons populate each of wells periodically. At comparatively large amplitudes of the harmonic drive, the dynamics show features of chaos in phase-space representation. For the chirped drive with a driving frequency increasing linearly in time, the imbalance of the atoms in the seesaw, however, has a temporal evolution that is faster for certain frequency ranges. The tunneling dynamics in such cases, for small amplitudes, show the appearance of quasi-periodicity with simultaneously present slow and fast oscillations. Increasing the amplitude of the chirped drive, we observe that the dynamics, although being periodic, become severely damped in their amplitude. Our study establishes that by tuning the temporal evolution of the quantum seesaw, a precise control of tunneling dynamics of the correlated bosons can be achieved. Since harmonic driving and chirp frequency modulation of the seesaw are experimentally achievable, our simulations can be experimentally realized in laboratories dealing with cold atomic gases.

David F. P. Pile

Kafkas M. Caprazli

A pedagogical parable illustrating the second complementarity relation for gravitational decoherence. Two children on a seesaw discover their pivot height has shifted evidence their seesaw rests on a master seesaw, with another seesaw at its far end. Their seesaw’s tilt (left-right) is perpendicular to the master’s tilt (up-down); balance reveals the master structure. The master angle θC = arctan(μC/S) encodes the ratio of hidden to known contributions. When hidden equals known, both the seesaw balance angle and the master tilt equal 45—a double-45 structure reflecting equal partition on orthogonal axes.

Christoph Maschler, Helmut Ritsch, András Vukics +1 more

Atom-field entanglement is shown to play a crucial role for the onset of spatial self-organization of ultracold atoms in an optical lattice within a high-Q cavity. Like particles on a seesaw, the atoms feel a different potential depending on their spatial distribution. The system possesses two stable configurations, where all atoms occupy either only even or only odd lattice sites. While for a classical cavity field description a distribution balanced between even and odd sites is a stationary equilibrium state at zero temperature, the possibility of atom-field entanglement in a quantum field description yields an instant simultaneous decay of the homogeneous atomic cloud into an entangled superposition of the two stable atomic patterns correlated with different cavity fields. This effect could be generic for a wide class of quantum phase transitions, whenever the quantum state can act back on the control parameter.

Oskar J. Painter