Institute for Quantum Studies
Schmid College of Science and Technology
Prototype experiment: Howell lab, Rochester
PRL 102, 173601 (2009)
Ultra-sensitive to beam deflection: ~560 femto-radians of tilt detected
(Small tilt is amplified in the signal by the small phase offset from a perfect dark port)
Penalty: output intensity strongly attenuated
Angular tilt (transverse momentum) amplified by large weak value.
Gaussian profile of beam becomes modulated.
JD et al., PRA 88, 023801 (2013)
Left: Wavefront tilt mechanism producing spatial modulation
Right: Asymmetric dark port profiles in different regimes
Dashed envelope: input beam intensity
dark port intensity
weak value regime
double lobe regime
Dark port has single lobe that approximates displaced a Gaussian centered at:
Tiny beam deflections can be distinguished, but with low output intensity.
Raw split-detected signal has linear response around .
Changing just attenuates the observable signal at the meter.
(Parameter-invariant response curves)
Renormalizing by the collected power sharpens the linear response to a
region bounded by .
The slope of this response involves an anomalously large weak value.
Mirror vertically misaligned to produce phase shift
Frequency-dependent horizontal tilt
Frequency-modulated and power-locked source laser
Prototype experiment: Howell lab, Rochester, PRA 82, 063822 (2010)
Idea: Use prism to convert frequency modulation into beam tilt
(weak value regime)
Spectral density of split detected signal
WVA vs. Focused spot
Two injected noise sources:
Prototype experiment: Howell lab, Rochester, PRA 92, 032127 (2015)
Goal: compare robustness against technical noise for two theoretically similar (and near optimal) beam deflection techniques
(Real noise in the wild)
Consider an input signal with ~12,000 photons per modulation cycle. After post-selection, WV has only ~120 photons remaining per cycle.
With such a small signal, shot noise becomes visible.
Nevertheless, the WV technique performs equally well.
An input signal with ~120 photons per modulation cycle.
After post-selection, WV keeps only ~1.2 photons per cycle.
The shot noise sampling drops below the Nyquist limit.
Averaging over many integration periods still compensates.
Even including incoherent background light incident on the detector,
the detection scales identically between a standard focused spot as more photons are added per cycle, in spite of the lower flux.
The incoherent background light incident degrades the visibility of the spectral information uniformly for both a focused spot and WV.
Averaging over multiple phase-locked integrations restores visibility.