Optical attenuation without absorption

Abstract

We consider a coherent state of light propagating through an ensemble of two-level atoms where all the atoms are initially in their ground state. In ordinary absorption, the transition of atoms to their excited state along with the absorption of a photon will remove energy from the beam and attenuate the signal. Here we show that post-selecting on those cases in which none of the atoms made a transition to the excited state can give even more attenuation than would normally occur due to absorption. The same process can also produce amplification when there is a sufficiently strong interaction between the photons and the atoms.

Generating photon-added states without adding a photon

“…Nevertheless, the post-selection process can change the probability amplitudes n c of the state in a number-state basis, since different values of n will have different probability amplitudes for producing the post-selected output. In that respect, these results are somewhat similar to an earlier paper [31] in which we considered postselecting on an ensemble of absorbing atoms, accepting only those events in which the atoms remained in their ground states. Although the atoms may appear to have done nothing, the post-selection process can increase the amount of absorption or even produce gain, depending on the strength of the interaction.…”

Generating photon-added states without adding a photon

“…Nevertheless, the post-selection process can change the probability amplitudes n c of the state in a number-state basis, since different values of n will have different probability amplitudes for producing the post-selected output. In that respect, these results are somewhat similar to an earlier paper [31] in which we considered post-selecting on an ensemble of absorbing atoms, accepting only those events in which the atoms remained in their ground states.…”

Inhibiting phase drift in multi-atom clocks using the quantum Zeno effect

“…It has also been shown that the Zeno effect is a sufficient resource for the implementation of quantum logic gates 20,21 , which could be used as the basis of a quantum computer 21 or quantum repeaters 22 . The Zeno effect can also be used to prepare various nonclassical or entangled states [23][24][25][26][27] and to protect entanglement once it has been generated 28,29 . The anti-Zeno effect, by which repeated measurements increase the rate of transitions, may be useful in quantum heat engines 30 .…”