Scalable quantum technologies require faithful conversion between matter qubits storing the quantum information and photonic qubits carrying the information in integrated circuits and waveguides. We demonstrate that the electromagnetic field chiralit
y which arises in nanophotonic waveguides leads to unidirectional emission from an embedded quantum dot quantum emitter, with resultant in-plane transfer of matter-qubit (spin) information. The chiral behavior occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We measure and compare the phenomena in single mode nanobeam and photonic crystal waveguides. The former is much more tolerant to dot position, exhibits experimental spin-path readout as high as 95 +/- 5% and has potential to serve as the basis of future spin-logic and network implementations.
We develop a novel statistical strong lensing approach to probe the cosmological parameters by exploiting multiple redshift image systems behind galaxies or galaxy clusters. The method relies on free-form mass inversion of strong lenses and does not
need any additional information other than gravitational lensing. Since in free-form lensing the solution space is a high-dimensional convex polytope, we consider Bayesian model comparison analysis to infer the cosmological parameters. The volume of the solution space is taken as a tracer of the probability of the underlying cosmological assumption. In contrast to parametric mass
The decoherence of a two-state tunneling molecule, such as a chiral molecule or ammonia, due to collisions with a buffer gas is analyzed in terms of a succession of quantum states of the molecule satisfying the conditions for a consistent family of h
istories. With $hbar omega$ the separation in energy of the levels in the isolated molecule and $gamma$ a decoherence rate proportional to the rate of collisions, we find for $gamma gg omega$ (strong decoherence) a consistent family in which the molecule flips randomly back and forth between the left- and right-handed chiral states in a stationary Markov process. For $gamma < omega$ there is a family in which the molecule oscillates continuously between the different chiral states, but with occasional random changes of phase, at a frequency that goes to zero at a phase transition $gamma = omega$. This transition is similar to the behavior of the inversion frequency of ammonia with increasing pressure, but will be difficult to observe in chiral molecules such as D$_2$S$_2$. There are additional consistent families both for $gamma > omega$ and for $gamma < omega$. In addition we relate the speed with which chiral information is transferred to the environment to the rate of decrease of complementary types of information (e.g., parity information) remaining in the molecule itself.
