Ramsey transfer fringe

Two pi/2-like pulses convert the phase accumulated during free evolution into near-complete population transfer to the second bound state.

QPE preset #22

This page describes the phenomenon using the current QPE preset and numerical modules as its primary source.

Physical idea

Ramsey physically separates creation of the superposition from phase readout. During free evolution the density may look almost unchanged, yet relative phase keeps accumulating and the second pulse converts it into population.

Key relation. π/2 pulse → free evolution → π/2 pulse. The free phase Δφ=Δω·T is converted into a measurable population fringe by the second pulse.

Guided protocol from the preset

First pulse. The system starts in the first double-well eigenstate. A short resonant linear-bias pulse acts as a pi/2 pulse and creates an almost 50/50 superposition of the two lowest states.

Free evolution. The drive is switched off for 5.5 time units. The viewport may look quiet, yet the two energy components keep accumulating relative phase.

Second pulse. An identical pulse recombines the amplitudes. With this waiting time, accumulated phase is converted almost completely into state-2 population.

Watch Analysis -> Ramsey. P1/P2 are projections of the real 2D psi; the lower scan varies only free-evolution time and reveals the Ramsey fringes predicted by the two-level subspace.

Compare. Load Return Fringe next: everything is identical except free-evolution time.

What to observe and how to study it

Run the guided preset unchanged and first identify the observable that changes.
Change one parameter at a time, then Reset and repeat.
Always compare rendering with the Analysis readouts: the image is a view, not a complete measurement.

History and experimental status

Norman Ramsey introduced the separated-oscillatory-fields method at the end of the 1940s; his 1950 paper formalized a technique that underlies precision spectroscopy, atomic clocks and quantum interferometry.

Representative physical scale

Representative platform	ultracold Rb-87 atom / trapped matter wave
Mapping basis	Rb-87 kinetic-unit mapping
1 QPE length unit	1 µm
1 QPE time unit	1.37 ms
Energy scale E₀=ħ/T₀	0.481 peV
Equivalent frequency E₀/h	0.116 kHz
Note	Representative cold-atom mapping. Trap frequencies, optical geometries and internal-state protocols set the actual laboratory scale; this mapping is intentionally order-of-magnitude.

The scale is an order-of-magnitude bridge from QPE dimensionless units to one plausible platform; it does not turn the preset into a quantitative simulation of that specific apparatus.

Essential references

N. F. Ramsey — A Molecular Beam Resonance Method with Separated Oscillating Fields (Phys. Rev. 78, 695 (1950))

Continue studying

Open Model & Constraints to see exactly what QPE computes and what is left outside the model. For current live values use Help → Current Experiment → Current Parameters.