Generation of bright squeezed vacuum in the Karassiov states
M. V. Chekhova,
T. Sh. Iskhakov,
G. Leuchs,
G. O. Rytikov
OPTICS AND SPECTROSCOPY
111
(4)
565-569
(2011)
| Journal
We suggest an experimental procedure allowing one to prepare squeezed vacuum in a special type of generalized Bell states, first introduced by V.P. Karassiov. We present the first results on the experimental generation of such states and observation of their polarization properties.
Absolute calibration of photodetectors: photocurrent multiplication
versus photocurrent subtraction
I. N. Agafonov,
M. V. Chekhova,
T. S. Iskhakov,
A. N. Penin,
G. O. Rytikov,
O. A. Shcherbina
OPTICS LETTERS
36
(8)
1329-1331
(2011)
We report testing of the new absolute method of photodetector calibration based on the difference-signal measurement for two-mode squeezed vacuum by comparison with the traditional absolute method based on coincidence counting. Using low-gain parametric downconversion, we have measured the quantum efficiency of a counting detector by both methods. The difference-signal method was adapted for the counting detectors by taking into account the dead-time effect. (c) 2011 Optical Society of America
Accessing photon bunching with a photon number resolving multi-pixel
detector
Dmitry A. Kalashnikov,
Si Hui Tan,
Maria V. Chekhova,
Leonid A. Krivitsky
In quantum optics and its applications, there is an urgent demand for photon-number resolving detectors. Recently, there appeared multi-pixel counters (MPPC) that are able to distinguish between 1,2,..10 photons. At the same time, strong coupling between different pixels (crosstalk) hinders their photon-number resolution. In this work, we suggest a method for 'filtering out' the crosstalk effect in the measurement of intensity correlation functions. The developed approach can be expanded to the analysis of higher-order intensity correlations by using just a single MPPC. (C) 2011 Optical Society of America
Polarization properties of macroscopic Bell states
Timur Sh. Iskhakov,
Ivan N. Agafonov,
Maria V. Chekhova,
Georgy O. Rytikov,
Gerd Leuchs
The four two-photon polarization Bell states are one of the main instruments in the toolbox of quantum optics and quantum information. In our experiment we produce their multiphoton counterparts, macroscopic Bell states. These are relevant to applications in quantum technologies because they provide efficient interactions with material quantum objects and with each other via nonlinear interactions. Furthermore, we study the polarization properties of these states using the concept of second-order degree of polarization and its higher-order generalization.
COMPARATIVE TEST OF TWO METHODS OF QUANTUM EFFICIENCY ABSOLUTE
MEASUREMENT BASED ON SQUEEZED VACUUM DIRECT DETECTION
I. N. Agafonov,
M. V. Chekhova,
A. N. Penin,
G. O. Rytikov,
O. A. Shumilkina,
T. Sh Iskhakov
INTERNATIONAL JOURNAL OF QUANTUM INFORMATION
9
251-262
(2011)
| Journal
We realize and test in experiment a method recently proposed for measuring absolute quantum efficiency of analog photodetectors. Similar to the traditional (Klyshko) method of absolute calibration, the new one is based on the direct detection of two-mode squeezed vacuum at the output of a traveling wave OPA. However, in the new method, one measures the difference-photocurrent variance rather than the correlation function of photocurrents (number of coincidences), which makes the technique applicable for high-gain OPA. In this work we test the new method versus the traditional one for the case of photon-counting detectors where both techniques are valid.
Systematic analysis of signal-to-noise ratio in bipartite ghost imaging
with classical and quantum light
G. Brida,
M. V. Chekhova,
G. A. Fornaro,
M. Genovese,
E. D. Lopaeva,
I. Ruo Berchera
We present a complete and exhaustive theory of signal-to-noiseratio in bipartite ghost imaging with classical (thermal) and quantum (twin beams) light. The theory is compared with experiment for both twin beams and thermal light in a certain regime of interest.
Intensity correlations of thermal light
T. Iskhakov,
A. Allevi,
D. A. Kalashnikov,
V. G. Sala,
M. Takeuchi,
M. Bondani,
M. Chekhova
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
199
(1)
127-138
(2011)
| Journal
We demonstrate measurement of normalized Glauber's intensity correlation functions of different orders using an array photodetector. As the light source, we use a laser beam scattered by a rotating ground-glass disc, which has statistics close to that of thermal light. We compare the measurements of the normalized correlation functions to that of the difference-intensity variance and show that they are in a certain sense complementary. The independence of the variance measurement on the number of temporal modes has been demonstrated for the first time. Different versions of high-order ghost imaging are also realized and characterized quantitatively.
Macroscopic Pure State of Light Free of Polarization Noise
Timur Sh. Iskhakov,
Maria V. Chekhova,
Georgy O. Rytikov,
Gerd Leuchs
The preparation of completely nonpolarized light is seemingly easy; an everyday example is sunlight. The task is much more difficult if light has to be in a pure quantum state, as required by most quantum-technology applications. The pure quantum states of light obtained so far are either polarized or, in rare cases, manifest hidden polarization; even if their intensities are invariant to polarization transformations, higher-order moments are not. We experimentally demonstrate the preparation of the macroscopic singlet Bell state, which is pure, is completely nonpolarized, and has no polarization noise. Simultaneous fluctuation suppression in three Stokes observables below the shot-noise limit is demonstrated, opening perspectives for noiseless polarization measurements. The state is shown to be invariant to polarization transformations. This robust highly entangled isotropic state promises to fuel important applications in photonic quantum technologies.
Kontakt
Forschungsgruppe Maria Chekhova
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen
