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The wavefunction is the complex distribution used to completely describe a quantum system, and is central to quantum theory. But despite its fundamental role, it is typically introduced as an abstract element of the theory with no explicit definition. Rather, physicists come to a working understanding of the wavefunction through its use to calculate(More)
Recent work by Lundeen et al. [Nature (London) 474, 188 (2011)] directly measured the wave function by weakly measuring a variable followed by a normal (i.e., "strong") measurement of the complementary variable. We generalize this method to mixed states by considering the weak measurement of various products of these observables, thereby providing the(More)
We report on measurements of quantum electrodynamic processes in an intense electromagnetic wave, where nonlinear eeects both multiphoton and vacuum polarization are prominent. Nonlinear Compton scattering and electron-positron pair production have been observed in collisions of 46.6 GeV and 49.1 GeV electrons of the Final Focus Test Beam at SLAC with(More)
In 1945, Dirac attempted to develop a “formal probability” distribution to describe quantum operators in terms of two noncommuting variables, such as position x and momentum p [Rev. Mod. Phys. 17, 195 (1945)]. The resulting quasiprobability distribution is a complete representation of the quantum state and can be observed directly in experiments. We measure(More)
We report on the collision of 1.5 ps (FWHM) laser pulses traversing at 17° a short ~7 ps (FWHM) 46.6 GeV electron bunch. The phase-locked system used to maintain the correct timing of the laser pulses and the appropriate diagnostics are described. The jitter between the laser and electron pulses is determined from the stability of the observed rate of(More)
We present a method for measuring the transverse electric field profile of a beam of light which allows for direct phase retrieval. The measured values correspond, within a normalization constant, to the real and imaginary parts of the electric field in a plane normal to the direction of propagation. This technique represents a self-referencing method for(More)
In a new experiment at the Final Focus Test Beam at SLAC a l o w-emittance 46.6-GeV electron beam is brought i n to collision with terawatt pulses from a 1.06-m-wavelength Nd:glass laser. Peak laser intensities of 10 18 WWcm 2 have been achieved corresponding to a value of 0.6 for the parameter = eE=m! 0 c, and to a value of 0.3 for the parameter = E ? =E(More)
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