Longzhu Cen

Ultra-sensitive and super-resolving angular rotation measurement based on photon orbital angular momentum using parity measurement.

Photon orbital angular momentum has led to many novel insights and applications in quantum measurement. Photon orbital angular momentum can increase the resolution and sensitivity of angular rotation measurement. However, quantum measurement strategy can further surpass this limit and improve the resolution of angular rotation measurement. This Letter proposes and demonstrates a parity measurement method in angular rotation measurement scheme for the first time. Parity measurement can make the resolution superior to the limit of the existing method. The sensitivity can be improved with higher orbital angular momentum photons. Moreover, this Letter gives a detailed discussion of the change of resolution and sensitivity in the presence of photon loss.

Super-resolving angular rotation measurement using binary-outcome homodyne detection.

There has been much recent interest in high precision angular rotation measurement using photon orbital angular momentum to realize super-resolving angular rotation measurement. It is well known that quantum detection strategies can obtain a quantum-enhanced performance. Here, we prove that binary-outcome homodyne detection method can obtain a narrower signal peak, showing better resolution compared with the existing data processing method. Since the photon loss is unavoidable in the actual non-ideal optical system, this paper further discusses the impact of photon loss on the resolution and sensitivity of angular rotation measurement with binary-outcome homodyne detection method.

Toward performing angular rotating measure of Heisenberg scaling by using the four-photon Holland-Burnett state

Quantum process tomography, as an advanced means of metrology, has a capacious range of applications for estimating numerous meaningful parameters. The parameter estimate precision of using coherent state and single photon state as probe are limited by the shot noise limit. Here we demonstrate a quantum enhanced rotating angle measure scheme based on the four-photon Holland-Burnett state can achieve the Heisenberg scaling by the coincidence counting technology. At the same time, the output signal of our scheme has an 8-fold super-resolution compared to the Malus law. In addition, the accuracy achieved by four photons is consistent with using 12 photons of single photon probe. That has incomparable preponderance in a situation in which only weak light can be exploited, like the measure of frangible biological specimens and photosensitive crystals. Moreover, the four-photon Holland-Burnett state can be generated by a polarization-entangled light source. These ensure that our scheme has a champaign application prospect.

Effects of imperfect elements on resolution and sensitivity of quantum metrology using two-mode squeezed vacuum state

It has been demonstrated that using two-mode squeezed vacuum state for phase estimation can break the Heisenberg limit. Our results reveal that the two-mode squeezed vacuum state is also applied to the optical rotation angle measurement. In our scheme, the resolution and sensitivity of the optical rotation angle signal are the same as the case of phase estimation. For the parameter estimation, phase or rotation angle, we discuss the influences of several imperfect factors on the resolution and sensitivity. First, the effect that the upper limit of photon-number resolving has on the maximum amount of available quantum Fisher information has been analyzed. Then, we have also studied the impacts of both the transmission efficiency in the transmission process and the detection efficiency on the detection results. Finally, conditions where all of the above imperfect elements are taken into account at the same time have also been explored. Additionally, other imperfect factors such as squeezing efficiency and dark counts are briefly discussed.

Super-resolving polarization rotation angle measurement using parity detection at shot noise limit

The polarization of the light is an excellent information carrier, but polarization information of coherent state in the quantum measurement of the past has not been clearly expressed. We refer to some ideas of quantum computation and quantum information, considering the polarization mode of the electromagnetic field to describe polarization information of a coherent state. And on this basis we put forward a polarization rotation angle measurement device based on a Mach-Zehnder interferometer and two polarizers. We also consider the intensity detection, parity detection and Z detection as detection strategies. The results show that this device can realize the super-resolution and shot noise limit with parity detection and Z detection. By simulation analysis, we finally find parity detection is the best method for our scheme, and we also discuss the effects of some parameters on sensitivity and resolution with parity detection.

Super-resolution and super-sensitivity of entangled squeezed vacuum state using optimal detection strategy

Interference metrology is a method for achieving high precision detection by phase estimation. The phase sensitivity of a traditional interferometer is subject to the standard quantum limit, while its resolution is constrained by the Rayleigh diffraction limit. The resolution and sensitivity of phase measurement can be enhanced by using quantum metrology. We propose a quantum interference metrology scheme using the entangled squeezed vacuum state, which is obtained using the magic beam splitter, expressed as , such as the N00N state. We derive the phase sensitivity and the resolution of the system with Z detection, project detection, and parity detection. By simulation and analysis, we determine that parity detection is an optimal detection method, which can break through the Rayleigh diffraction limit and the standard quantum limit.

Photon counting chirped amplitude modulation lidar using an asymmetric triangular wave modulation

We propose a novel strategy of asymmetric triangular-wave modulation for photon-counting chirped amplitude modulation (PCCAM) lidar. Earlier studies use the symmetric triangle wave modulation, by which the velocity can be detected only when the Doppler shift caused by a moving target is greater than Full Width Half Maximum (FWHM) of Intermediate Frequency (IF). We use an alternative method known as the asymmetric triangular wave modulation method, in which the modulation rates of the up-ramp and the down-ramp are different. This new method avoids the overlapping of the up-ramp and the down-ramp IF peaks, and breaks the limit of the FWHM of IF peak to improve the velocity measuring sensitivity (also called the minimum detectable velocity). Finally, a proof-of-principle experiment is carried out in the laboratory. The experimental results agree well with the theoretical results and show the improvement of the minimum detectable velocity.