In an unseeded SU(1,1) interferometer composed of two cascaded degenerate parametric amplifiers, with direct detection at the output, we demonstrate a phase sensitivity overcoming the shot noise limit by 2.3 dB. The interferometer is strongly unbalanced, with the parametric gain of the second amplifier exceeding the gain of the first one by a factor of 2, which makes the scheme extremely tolerant to detection losses. We show that by increasing the gain of the second amplifier, the phase supersensitivity of the interferometer can be preserved even with detection losses as high as 80%. This finding can considerably improve the state-of-the-art interferometry, enable sub-shot-noise phase sensitivity in spectral ranges with inefficient detection, and allow extension to quantum imaging.The sensitivity of an interferometric measurement on a phase shift depends on the state of light used as a probe and the measurement scheme. A 'standard' precision is provided by a coherent state fed into a Mach-Zender interferometer, the socalled shot noise limit (SNL). A measurement beating this limit is said to be supersensitive. In order to make super-sensitive phase measurements, quantum resources can be used. First proposed [1] and experimentally tested [2,3] in the 1980-s, squeezed light is now used for gravitational wave detection [4,5] beyond the shot noise limit. Squeezed states can improve the sensitivity in the presence of loss [6], a finite interference visibility [7] and their use is compatible with power recycling [8]. Supersensitivity can also be achieved with other quantum states [9,10], which, however, are difficult to produce.Besides the input state and the detection scheme, one can also modify the interferometer. Yurke et al. [11] proposed to use cascaded optical parametric amplifiers (OPAs) instead of the passive beamsplitters of conventional interferometric setups, the phase sensitive response of the OPAs giving rise to interference patterns. Such interferometers, usually called SU(1,1) interferometers, can display phase super-sensitivity without seeding the amplifiers [11]. Seeding can be used in order to increase the number of sensing photons and therefore the overall sensitivity [12]. It was recently noted theoretically that such a scheme involving two amplifiers can help overcoming the deleterious effects of optical losses [13,14] on phase sensitivity. Note that losses occurring inside the interferometer have a different impact on the phase sensitivity than losses outside of the interferometer. These two kinds of losses are therefore distinguished in the following and respectively called internal and external/detection losses. The influence of the latter kind of losses can be suppressed by the second amplifier. Indeed, amplifying the signal with the second OPA at the output of the interferometer while keeping the probing field constant eventually eliminates the effect of detection losses [15,16].Optical SU(1,1) interferometers have been implemented using two cascaded four-wave mixers [17,18]. Recent experiment...

We present a method that allows determining the band-edge exciton fine structure of CdSe/CdS dot-in-rods samples based on single particle polarization measurements at room temperature. We model the measured emission polarization of such single particles considering the fine structure properties, the dielectric effect induced by the anisotropic shell, and the measurement configuration. We use this method to characterize the band-edge exciton fine structure splitting of various samples of dot-in-rods. We show that, when the diameter of the CdSe core increases, a transition from a spherical like band-edge exciton symmetry to a rod-like band edge exciton symmetry occurs. This explains the often reported large emission polarization of such particles compared to spherical CdSe/CdS emitters.