IQI Weekly Seminar

ABSTRACT:

  Injecting quantum particles into a multichannel interferometer is a mainstay for photonic quantum information processing, exploring foundational issues in quantum mechanics and striving for arguably the first demonstration of quantum supremacy via the BosonSampling problem. Typical analyses assume particle indistinguishability including simultaneity of particle arrival times, and boson permutational symmetry yields coincidence rates that scale with permanents of submatrices of the interferometer transition matrix.  We show that partial particle distinguishability leads to coincidence rates that depend on all immanants, which interpolate between the efficiently calculated determinant and the #P-Hard permanent of a matrix. As controllable distinguishability is essential for calibrating the interferometry, the role of immanants is fundamentally interesting, and our result leads to the counterintuitive conclusion that simulating fermionic interferometry is computationally hard.