文档介绍：Observation of the Dynamical Casimir Effect in a
Superconducting Circuit
. Wilson1,G. Johansson1, A. Pourkabirian1, .
Johansson2, T. Duty3, F. Nori2,4 & P. Delsing1
1Depart. of Microtechnology and Nanoscience,
Chalmers University of Technology, G¨, Sweden
2Advanced Science Institute, RIKEN,
Wako-shi, Saitama 351-0198, Japan
3University of New South Wales, Sydney, NSW, 2052 Australia and
4University of Michigan, Ann Arbor, MI 48109, USA
(Dated: May 25, 2011)
PACS numbers:
arXiv: [quant-ph] 24 May 2011
1
One of the most surprising predictions of modern quantum theory is that the vacuum of
space is not empty. In fact, quantum theory predicts that it teems with virtual particles
flitting in and out of existence. While initially a curiosity, it was quickly realized that these
vacuum fluctuations had measurable consequences, for instance producing the Lamb shift[1]
of atomic spectra and modifying the ic moment for the electron[2]. This type of
renormalization due to vacuum fluctuations is now central to our understanding of nature.
However, these effects provide indirect evidence for the existence of vacuum fluctuations.
From early on, it was discussed if it might instead be possible to more directly observe
the virtual particles pose the quantum vacuum. 40 years ago, Moore[3] suggested
that a mirror undergoing relativistic motion could convert virtual photons into directly
observable real photons. This effect was later named the dynamical Casimir effect (DCE).
Using a superconducting circuit, we have observed the DCE for the first time. The circuit
consists of a coplanar transmission line with an electrical length that can be changed at a
few percent of the speed of light. The length is changed by modulating the inductance of
a superconducting quantum interference device (SQUID) at high frequencies (∼ 11 GHz).
In addition to observing the creation of real photons, we observe two-mode squeezing of the
emitted r