The Creation and Detection of Arbitrary Photon Number States Using Cavity QED

No description supplie

Topological State Reconstruction For Wireless Stabilization of Distant Atomic Clocks

High-precision frequency alignment with classical communication channels is difficult due to noise, propagation delays, and signal degradation. Current optical methods, commonly involving frequency combs, are capable of synchronising clocks with exceptional precision up to the region of a part in 10e20. Alternatively, wireless methods see use where this is not practical, with achievable precision within the nanosecond region. This leaves few options for achieving high-precision clock synchronisation without requiring specialised equipment, a fibre connection, or a line of sight communication channel. Here we present a novel approach combining quantum state reconstruction with feedback controls to stabilize the frequency of two atomic clocks separated by a 900 MHz free space radio link. Quantum state reconstruction enables tracking of phase and frequency fluctuations during transmission. We see that a part in 10e16 precision in frequency alignment of the clocks can be achieved using commonly-available radio equipment, allowing precise timekeeping and synchronization over long distances provided a radio communications channel can be established, with potential applications in a wide variety of timekeeping applications.Comment: 5 pages, 4 Figure

Generating Photon Number States on Demand via Cavity Quantum Electrodynamics

No description supplie

Quantum Secrecy in Thermal States

We propose to perform quantum key distribution using quantum correlations occurring within thermal states produced by low power sources such as LED's. These correlations are exploited through the Hanbury Brown and Twiss effect. We build an optical central broadcast protocol using a superluminescent diode which allows switching between laser and thermal regimes, enabling us to provide experimental key rates in both regimes. We provide a theoretical analysis and show that quantum secrecy is possible, even in high noise situations.Comment: This version includes revisions prompted by referees comments, and some other small editorial comment

Internal-quantum-state engineering using magnetic fields

We present a general, semi-classical theory describing the interaction of an atom with an internal state consisting of a number of degenerate energy levels with static and oscillating magnetic fields. This general theory is applied to the 3P2 metastable energy level of neon to determine the dynamics of the populations and coherences that are formed due to the interaction. Through these calculations we demonstrate how the interaction may be used for the internal state preparation of an atom

Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime

We carry out a theoretical investigation on the collective dynamics of an ensemble of correlated atoms, subject to both vacuum fluctuations of spacetime and stochastic gravitational waves. A general approach is taken with the derivation of a quantum master equation capable of describing arbitrary confined nonrelativistic matter systems in an open quantum gravitational environment. It enables us to relate the spectral function for gravitational waves and the distribution function for quantum gravitational fluctuations and to indeed introduce a new spectral function for the zero-point fluctuations of spacetime. The formulation is applied to two-level identical bosonic atoms in an off-resonant high-Q cavity that effectively inhibits undesirable electromagnetic delays, leading to a gravitational transition mechanism through certain quadrupole moment operators. The overall relaxation rate before reaching equilibrium is found to generally scale collectively with the number N of atoms. However, we are also able to identify certain states of which the decay and excitation rates with stochastic gravitational waves and vacuum spacetime fluctuations amplify more significantly with a factor of N². Using such favorable states as a means of measuring both conventional stochastic gravitational waves and novel zero-point spacetime fluctuations, we determine the theoretical lower bounds for the respective spectral functions. Finally, we discuss the implications of our findings on future observations of gravitational waves of a wider spectral window than currently accessible. Especially, the possible sensing of the zero-point fluctuations of spacetime could provide an opportunity to generate initial evidence and further guidance of quantum gravity