90 research outputs found
Stable control of 10 dB two-mode squeezed vacuum states of light
Continuous variable entanglement is a fundamental resource for many quantum
information tasks. Important protocols like superactivation of zero-capacity
channels and finite-size quantum cryptography that provides security against
most general attacks, require about 10 dB two-mode squeezing. Additionally,
stable phase control mechanisms are necessary but are difficult to achieve
because the total amount of optical loss to the entangled beams needs to be
small. Here, we experimentally demonstrate a control scheme for two-mode
squeezed vacuum states at the telecommunication wavelength of 1550 nm. Our
states exhibited an Einstein-Podolsky-Rosen covariance product of 0.0309 \pm
0.0002, where 1 is the critical value, and a Duan inseparability value of 0.360
\pm 0.001, where 4 is the critical value. The latter corresponds to 10.45 \pm
0.01 dB which reflects the average non-classical noise suppression of the two
squeezed vacuum states used to generate the entanglement. With the results of
this work demanding quantum information protocols will become feasible.Comment: 8 pages, 4 figure
Strong Einstein-Podolsky-Rosen steering with unconditional entangled states
In 1935 Schr\"odinger introduced the terms entanglement and steering in the
context of the famous gedanken experiment discussed by Einstein, Podolsky, and
Rosen (EPR). Here, we report on a sixfold increase of the observed EPR-steering
effect as quantified by the Reid-criterion. We achieved an unprecedented low
conditional variance product of about 0.04 < 1, where 1 is the upper bound
below which steering is present. The steering effect was observed on an
unconditional two-mode-squeezed entangled state that contained a total vacuum
state contribution of less than 8%, including detection imperfections. Together
with the achieved high interference contrast between the entangled state and a
bright coherent laser field, our state is compatible with efficient
applications in high-power laser interferometers and fiber-based networks for
entanglement distribution.Comment: 5 pages, 3 figure
Squeezed light at 1550 nm with a quantum noise reduction of 12.3 dB
Continuous-wave squeezed states of light at the wavelength of 1550 nm have
recently been demonstrated, but so far the obtained factors of noise
suppression still lag behind today's best squeezing values demonstrated at 1064
nm. Here we report on the realization of a half-monolithic nonlinear resonator
based on periodically-poled potassium titanyl phosphate which enabled the
direct detection of up to 12.3 dB of squeezing at 5 MHz. Squeezing was observed
down to a frequency of 2 kHz which is well within the detection band of
gravitational wave interferometers. Our results suggest that a long-term stable
1550 nm squeezed light source can be realized with strong squeezing covering
the entire detection band of a 3rd generation gravitational-wave detector such
as the Einstein Telescope
Strong Einstein-Podolsky-Rosen entanglement from a single squeezed light source
Einstein-Podolsky-Rosen (EPR) entanglement is a criterion that is more
demanding than just certifying entanglement. We theoretically and
experimentally analyze the low resource generation of bi-partite continuous
variable entanglement, as realized by mixing a squeezed mode with a vacuum mode
at a balanced beam splitter, i.e. the generation of so-called vacuum-class
entanglement. We find that in order to observe EPR entanglement the total
optical loss must be smaller than 33.3 %. However, arbitrary strong EPR
entanglement is generally possible with this scheme. We realize continuous wave
squeezed light at 1550 nm with up to 9.9 dB of non-classical noise reduction,
which is the highest value at a telecom wavelength so far. Using two phase
controlled balanced homodyne detectors we observe an EPR co-variance product of
0.502 \pm 0.006 < 1, where 1 is the critical value. We discuss the feasibility
of strong Gaussian entanglement and its application for quantum key
distribution in a short-distance fiber network.Comment: 4 pages, 4 figure
Realization of finite-size quantum key distribution based on Einstein-Podolsky-Rosen entangled light
[no abstract
Experimental entanglement distribution by separable states
The distribution of entanglement between macroscopically separated parties
represents a crucial protocol for future quantum information networks.
Surprisingly, it has been theoretically shown that two distant systems can be
entangled by sending a third mediating system that is not entangled with either
of them. Such a possibility seems to contradict the intuition that to
distribute entanglement, the transmitted system always needs to be entangled
with the sender. Here, we experimentally distribute entanglement by exchanging
a subsystem and successfully prove that this subsystem is not entangled with
either of the two parties. Our implementation relies on the preparation of a
specific three-mode Gaussian state containing thermal noise that demolishes the
entanglement in two of the three bipartite splittings. After transmission of a
separable mode this noise can be removed by quantum interference. Our work
demonstrates an unexpected variant of entanglement distribution and improves
the understanding necessary to engineer multipartite quantum information
networks.Comment: 9 pages, 6 figure
Enhanced Apoptosis and Loss of Cell Viability in Melanoma Cells by Combined Inhibition of ERK and Mcl-1 Is Related to Loss of Mitochondrial Membrane Potential, Caspase Activation and Upregulation of Proapoptotic Bcl-2 Proteins
Targeting of MAP kinase pathways by BRAF inhibitors has evolved as a key therapy for BRAF-mutated melanoma. However, it cannot be applied for BRAF-WT melanoma, and also, in BRAF-mutated melanoma, tumor relapse often follows after an initial phase of tumor regression. Inhibition of MAP kinase pathways downstream at ERK1/2, or inhibitors of antiapoptotic Bcl-2 proteins, such as Mcl-1, may serve as alternative strategies. As shown here, the BRAF inhibitor vemurafenib and the ERK inhibitor SCH772984 showed only limited efficacy in melanoma cell lines, when applied alone. However, in combination with the Mcl-1 inhibitor S63845, the effects of vemurafenib were strongly enhanced in BRAF-mutated cell lines, and the effects of SCH772984 were enhanced in both BRAF-mutated and BRAF-WT cells. This resulted in up to 90% loss of cell viability and cell proliferation, as well as in induction of apoptosis in up to 60% of cells. The combination of SCH772984/S63845 resulted in caspase activation, processing of poly (ADP-ribose) polymerase (PARP), phosphorylation of histone H2AX, loss of mitochondrial membrane potential, and cytochrome c release. Proving the critical role of caspases, a pan-caspase inhibitor suppressed apoptosis induction, as well as loss of cell viability. As concerning Bcl-2 family proteins, SCH772984 enhanced expression of the proapoptotic Bim and Puma, as well as decreased phosphorylation of Bad. The combination finally resulted in downregulation of antiapoptotic Bcl-2 and enhanced expression of the proapoptotic Noxa. In conclusion, combined inhibition of ERK and Mcl-1 revealed an impressive efficacy both in BRAF-mutated and WT melanoma cells, and may thus represent a new strategy for overcoming drug resistance
Quantum Enhancement of the Zero-Area Sagnac Interferometer Topology for Gravitational Wave Detection
Only a few years ago, it was realized that the zero-area Sagnac
interferometer topology is able to perform quantum nondemolition measurements
of position changes of a mechanical oscillator. Here, we experimentally show
that such an interferometer can also be efficiently enhanced by squeezed light.
We achieved a nonclassical sensitivity improvement of up to 8.2 dB, limited by
optical loss inside our interferometer. Measurements performed directly on our
squeezed-light laser output revealed squeezing of 12.7 dB. We show that the
sensitivity of a squeezed-light enhanced Sagnac interferometer can surpass the
standard quantum limit for a broad spectrum of signal frequencies without the
need for filter cavities as required for Michelson interferometers. The Sagnac
topology is therefore a powerful option for future gravitational-wave
detectors, such as the Einstein Telescope, whose design is currently being
studied.Comment: 4 pages, 4 figure
Gaussian entanglement for quantum key distribution from a single-mode squeezing source
We report the suitability of an Einstein-Podolsky-Rosen entanglement source for Gaussian continuous-variable quantum key distribution at 1550 nm. Our source is based on a single continuous-wave squeezed vacuum mode combined with a vacuum mode at a balanced beam splitter. Extending a recent security proof, we characterize the source by quantifying the extractable length of a composable secure key from a finite number of samples under the assumption of collective attacks. We show that distances in the order of 10 km are achievable with this source for a reasonable sample size despite the fact that the entanglement was generated including a vacuum mode. Our security analysis applies to all states having an asymmetry in the field quadrature variances, including those generated by superposition of two squeezed modes with different squeezing strengths.EU/FP7/Q-ESSENCEHALOSTARDFG/WE-1240/12-1BMBF/QUOREPJapan Society for the Promotion of Science/KAKENHI/24-02793EU/FP7/COQUI
- …