Electronic structure of multilayer graphene

We study the electronic structure of multilayer graphene using a $\pi$-orbital continuum model with nearest-neighbor intralayer and interlayer tunneling. Using degenerate state perturbation theory, we show that the low-energy electronic structure of arbitrarily stacked graphene multilayers consists of chiral pseudospin doublets with a conserved chirality sum.Comment: 25 pages, 15 figures; Expanded version of PRB 77,155416 (2008), arXiv:0711.4333; Published in the proceedings of YKIS2007; Typos correcte

Squeezed states of light from an optical parametric oscillator

Squeezed states of the electromagnetic field are generated by degenerate parametric downconversion in a subthreshold optical parametric oscillator. Reductions in photocurrent noise greater than 60% (-4 dB) below the limit set by the vacuum fluctuations of the field are observed in a balanced homodyne detector. A quantitative comparison with theory suggests that the observed noise reductions result from a field that in the absence of avoidable linear attenuation would be squeezed more than tenfold. A degree of squeezing of approximately fivefold is inferred for the actual field emitted through one mirror of the optical parametric oscillator. An explicit demonstration of the Heisenberg uncertainty principle for the electromagnetic field is made from the measurements, which show that the field state produced by the downconversion process is a state of minimum uncertainty