Picosecond timing resolution detection of  -photons utilizing microchannel-plate detectors: experimental tests of quantum nonlocality and photon localization

Abstract

The concept and subsequent experimental verification of the proportionality between pulse amplitude and detector transit time for microchannel plate detectors is presented. This discovery has led to considerable improvement in the overall timing resolution for detection of high energy gamma photons. Utilizing a 22 Na positron source, a full width half maximum (FWHM) timing resolution of 138 ps has been achieved. This FWHM includes detector transit-time spread for both chevron-stack type detectors, timing spread due to uncertainties in annihilation location, all electronic uncertainty, and any remaining quantum mechanical uncertainty. The first measurement of the minimum quantum uncertainty in the time interval between detection of the two annihilation photons is reported. The experimental results give strong evidence against instantaneous spatial-localization of γ-photons due to measurement-induced nonlocal quantum wave-function collapse. The experimental results are also the first that imply momentum is conserved only after the quantum uncertainty in time has elapsed [H. Yukawa, Proc. Phys. -Math. Soc. Japan, 17, 48 (1935)].

Photon correlations in positron annihilation

“…After averaging over the unobserved positron injection time, the annihilation photon coincidence rate was found to be proportional to exp (−Γ |τ 1 − τ 2 |) where τ j is the photon emission time. This supports Irby's observation [4] that annihilation photon pulse width is limited by the Ps lifetime. Only the peak of the double exponential function is determined by the position of the positron source.…”

“…This is plausible because the most widely accepted viewpoint is that the minimum quantum uncertainty in time is zero due to detection-induced nonlocal collapse [4]. Irby measured the time interval between detection of the annihilation photons from a 22 N a source and obtained 123 ± 22 ps [4]. This is a surprising result since, in his experiment, the annihilation photons originate in a source a few mm thick and a photon travels almost 4 cm in air in this time.…”

“…equal to P given by (27). The probability density P is proportional to exp [−Γ (t 1 + t 2 − 2t 0 )], but Irby measured the distribution of t 1 − t 2 , and neither (27) nor the absolute square or Irby's wave function in [4] gives their probabilities directly. The resolution to this problem lies in averaging over the positron injection time, t 0 , that is not measured but must be earlier than both τ 1 and τ 2 .…”

“…To evaluate (16) we need where τ > (τ < ) is the larger (smaller) of τ 1 and τ 2 . Since according to (4) and (13) 2t…”

“…Recently it has been suggested that measurement of the arrival time difference between paired annihilation photons will improve signal to noise in medical imaging applications, leading to time of flight (TOF) PET [3]. This is plausible because the most widely accepted viewpoint is that the minimum quantum uncertainty in time is zero due to detection-induced nonlocal collapse [4]. Irby measured the time interval between detection of the annihilation photons from a 22 N a source and obtained 123 ± 22 ps [4].…”