56 research outputs found
Macroscopic quantum resonators (MAQRO): 2015 Update
Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schrödinger’s cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow addressing such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored ‘quantum-classical’ transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the 4th Cosmic Vision call for a medium-sized mission (M4) in 2014 of the European Space Agency (ESA) with a possible launch in 2025, and we review the progress with respect to the original MAQRO proposal for the 3rd Cosmic Vision call for a medium-sized mission (M3) in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfill the stringent environmental requirements for macroscopic quantum experiments
Chirped-pulse interferometry with finite frequency correlations
Chirped-pulse interferometry is a new interferometric technique encapsulating
the advantages of the quantum Hong-Ou-Mandel interferometer without the
drawbacks of using entangled photons. Both interferometers can exhibit
even-order dispersion cancellation which allows high resolution optical delay
measurements even in thick optical samples. In the present work, we show that
finite frequency correlations in chirped-pulse interferometry and
Hong-Ou-Mandel interferometry limit the degree of dispersion cancellation. Our
results are important considerations in designing practical devices based on
these technologies.Comment: 10 pages, 2 figure
Cavity cooling of an optically levitated nanoparticle
The ability to trap and to manipulate individual atoms is at the heart of
current implementations of quantum simulations, quantum computing, and
long-distance quantum communication. Controlling the motion of larger particles
opens up yet new avenues for quantum science, both for the study of fundamental
quantum phenomena in the context of matter wave interference, and for new
sensing and transduction applications in the context of quantum optomechanics.
Specifically, it has been suggested that cavity cooling of a single
nanoparticle in high vacuum allows for the generation of quantum states of
motion in a room-temperature environment as well as for unprecedented force
sensitivity. Here, we take the first steps into this regime. We demonstrate
cavity cooling of an optically levitated nanoparticle consisting of
approximately 10e9 atoms. The particle is trapped at modest vacuum levels of a
few millibar in the standing-wave field of an optical cavity and is cooled
through coherent scattering into the modes of the same cavity. We estimate that
our cooling rates are sufficient for ground-state cooling, provided that
optical trapping at a vacuum level of 10e-7 millibar can be realized in the
future, e.g., by employing additional active-feedback schemes to stabilize the
optical trap in three dimensions. This paves the way for a new light-matter
interface enabling room-temperature quantum experiments with mesoscopic
mechanical systems.Comment: 14 pages, 6 figure
Experimental bound entanglement in a four-photon state
Entanglement [1, 2] enables powerful new quantum technologies [3-8], but in
real-world implementations, entangled states are often subject to decoherence
and preparation errors. Entanglement distillation [9, 10] can often counteract
these effects by converting imperfectly entangled states into a smaller number
of maximally entangled states. States that are entangled but cannot be
distilled are called bound entangled [11]. Bound entanglement is central to
many exciting theoretical results in quantum information processing [12-14],
but has thus far not been experimentally realized. A recent claim for
experimental bound entanglement is not supported by their data [15]. Here, we
consider a family of four-qubit Smolin states [16], focusing on a regime where
the bound entanglement is experimentally robust. We encode the state into the
polarization of four photons and show that our state exhibits both entanglement
and undistillability, the two defining properties of bound entanglement. We
then use our state to implement entanglement unlocking, a key feature of Smolin
states [16].Comment: 10 pages, 6 figures. For a simultaneously submitted related work see
arXiv:1005.196
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