2000/08/31 by H. J. Kimble, Y. Levin, Yuri Levin +4 · 7 citations
Engineering · Physics and Astronomy · #Advanced Frequency and Time Standards #Geophysics and Sensor Technology #Pulsars and Gravitational Waves Research #gr-qc #quant-ph
paper · pdf · doi:10.1103/physrevd.65.022002
published as Phys.Rev. D65 (2002) 022002 · Submitted to Physical Review D; RevTeX manuscript with 16 figures; prints to 33 pages in Physical Review double column format. Minor revisions have been made in response to referee report
arxiv created 2001/09/03 · openalex publication_date 2001/12/26 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
The LIGO-II gravitational-wave interferometers (ca. 2006--2008) are designed to have sensitivities near the standard quantum limit (SQL) in the vicinity of 100 Hz. This paper describes and analyzes possible designs for subsequent LIGO-III interferometers that can beat the SQL. These designs are identical to a conventional broad band interferometer (without signal recycling), except for new input and/or output optics. Three designs are analyzed: (i) a squeezed-input interferometer (conceived by Unruh based on earlier work of Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is injected into the interferometer's dark port; (ii) a variational-output interferometer (conceived in a different form by Vyatchanin, Matsko and Zubova), in which homodyne detection with FD homodyne phase is performed on the output light; and (iii) a squeezed-variational interferometer with squeezed input and FD-homodyne output. It is shown that the FD squeezed-input light can be produced by sending ordinary squeezed light through two successive Fabry-P'erot filter cavities before injection into the interferometer, and FD-homodyne detection can be achieved by sending the output light through two filter cavities before ordinary homodyne detection. With anticipated technology (power squeeze factor e^\ensuremath-2R=0.1 for input squeezed vacuum and net fractional loss of signal power in arm cavities and output optical train \ensuremathε*=0.01) and using an input laser power Io in units of that required to reach the SQL (the planned LIGO-II power, ISQL), the three types of interferometer could beat the amplitude SQL at 100 Hz by the following amounts \ensuremathμ\ensuremath≡√Sh/√ShSQL and with the following corresponding increase V=1/\ensuremathμ3 in the volume of the universe that can be searched for a given noncosmological source: Squeezedinput---\ensuremathμ\ensuremath≃√e^\ensuremath-2R\ensuremath≃0.3 and V\ensuremath≃1/0.33\ensuremath≃30 using Io/ISQL=1. Variational\ensuremath-output---\ensuremathμ\ensuremath≃\ensuremathε*1/4\ensuremath≃0.3 and V\ensuremath≃30 but only if the optics can handle a ten times larger power: Io/ISQL\ensuremath≃1/√\ensuremathε*=10. Squeezedvarational---\ensuremathμ=1.3(e^\ensuremath-2R\ensuremathε*)1/4\ensuremath≃0.24 and V\ensuremath≃80 using Io/ISQL=1; and \ensuremathμ\ensuremath≃(e^\ensuremath-2R\ensuremathε*)1/4\ensuremath≃0.18 and V\ensuremath≃180 using Io/ISQL=√e^\ensuremath-2R/\ensuremathε*\ensuremath≃3.2.