Quantum phase properties of photon added and subtracted displaced Fock states

Quantum phase properties of photon added and subtracted displaced Fock states (and a set of quantum states which can be obtained as the limiting cases of these states) are investigated from a number of perspectives, and it is shown that the quantum phase properties are dependent on the quantum state engineering operations performed. Specifically, the analytic expressions for quantum phase distributions and angular $Q$ distribution as well as measures of quantum phase fluctuation and phase dispersion are obtained. The uniform phase distribution of the initial Fock states is observed to be transformed by the unitary operation (i.e., displacement operator) into non-Gaussian shape, except for the initial vacuum state. It is observed that the phase distribution is symmetric with respect to the phase of the displacement parameter and becomes progressively narrower as its amplitude increases. The non-unitary (photon addition/subtraction) operations make it even narrower in contrast to the Fock parameter, which leads to broadness. The photon subtraction is observed to be a more powerful quantum state engineering tool in comparison to the photon addition. Further, one of the quantum phase fluctuation parameters is found to reveal the existence of antibunching in both the engineered quantum states under consideration. Finally, the relevance of the engineered quantum states in the quantum phase estimation is also discussed, and photon added displaced Fock state is shown to be preferable for the task.Comment: Quantum phase properties of an engineered quantum state has been studied from various perspective

Implementation of coherent one way protocol for quantum key distribution up to an effective distance of 145 km

In the present work, we report experimental realization of an optical fiber based COW protocol for QKD in the telecom wavelength (1550 nm) where the attenuation in the optical fiber is minimum. A laser of 1550 nm wavelength, attenuator and intensity modulator is used for the generation of pulses having average photon number 0.5 and repetition rate of 500 MHz. The experiment is performed over 40 km, 80 km and 120 km of optical fiber and several experimental parameters like disclose rate, compression ratio, dead time and excess bias voltage of the detector are varied for all the cases (i.e., for 40 km, 80 km and 120 km distances) to observe their impact on the final key rate. Specifically, It is observed that there is a linear increase in the key rate as we decrease compression ratio or disclose rate. The key rate obtains its maximum value for least permitted values of disclose rate, compression ratio and dead time. It seems to remain stable for various values of excess bias voltage. While changing various parameters, we have maintained the quantum bit error rate (QBER) below 6%. The key rate obtained is also found to remain stable over time. Experimental results obtained here are also compared with the earlier realizations of the COW QKD protocol. Further, to emulate key rate at intermediate distances and at a distance larger than 120 km, an attenuator of 5 dB loss is used which can be treated as equivalent to 25 km of the optical fiber used in the present implementation. This has made the present implementation equivalent to the realization of COW QKD upto 145 km.Comment: COW protocol for QKD is implemente

Can we control the amount of useful nonclassicality in a photon added hypergeometric state?

Non-Gaussianity inducing operations are studied in the recent past from different perspectives. Here, we study the role of photon addition, a non-Gaussianity inducing operation, in the enhancement of nonclassicality in a finite dimensional quantum state, namely hypergeometric state with the help of some quantifiers and measures of nonclassicality. We observed that measures to characterize the quality of single photon source and anticlassicality lead to the similar conclusion, i.e., to obtain the desired quantum features one has to choose all the state parameters such that average photon numbers remains low. Wigner logarithmic negativity of the photon added hypergeometric state and concurrence of the two-mode entangled state generated at the output of a beamsplitter from this state show that nonclassicality can be enhanced by increasing the state parameter and photon number addition but decreasing the dimension of the state. In principle, decreasing the dimension of the state is analogous to holeburning and is thus expected to increase nonclassicality. Further, the variation of Wigner function not only qualitatively illustrates the same features as observed quantitatively through concurrence potential and Wigner logarithimic negativity, but illustrate non-Gaussianity of the quantum state as well.Comment: Quantification of nonclassicality enhancement due to photon addition and holeburning in finite dimesional quantum stat

Lower- and higher-order nonclassical properties of photon added and subtracted displaced Fock states

Nonclassical properties of photon added and subtracted displaced Fock states have been studied using various witnesses of lower- and higher-order nonclassicality. Compact analytic expressions are obtained for the nonclassicality witnesses. Using those expressions, it is established that these states and the states that can be obtained as their limiting cases (except coherent states) are highly nonclassical as they show the existence of lower- and higher-order antibunching and sub-Poissonian photon statistics, in addition to the nonclassical features revealed through the Mandel $Q_M$ parameter, zeros of Q function, Klyshko's criterion, and Agarwal-Tara criterion. Further, some comparison between the nonclassicality of photon added and subtracted displaced Fock states have been performed using witnesses of nonclassicality. This has established that between the two types of non-Gaussianity inducing operations (i.e., photon addition and subtraction) used here, photon addition influences the nonclassical properties more strongly. Further, optical designs for the generation of photon added and subtracted displaced Fock states from squeezed vacuum state have also been proposed.Comment: A comparative study of the nonclassicality present in photon added and subtracted displaced Fock states shows photon addition is generally preferable nonclassicality inducing operation, while subtraction also has advantage in some cases over additio

Deep Brain Stimulation Approach in Neurological Diseases

The technique was emanated in early 1960s; nowadays, deep brain stimulation (DBS) has become a huge practice in treatment of various movement disorders along with some psychiatric disorders. The advancement of DBS in different neurodegenerative diseases and managing patients with refractory brain disorders are closely related to the developments in technology. This development in regard with the device advancement along with the safe coupling of DBS to high-resolution imaging can help us to shape our knowledge in brain-wide networks and circuits linked with clinical aspects. DBS is found to be useful in learning and memory. On the contrary, traditional epilepsy surgeries are more complicated and technologically DBS is easier and more feasible. There are mild adverse effects of this DBS treatment, but a number of studies have shown positive treatment outcome with movement disorders and many kinds of psychiatric disorders too

One-shot learning for solution operators of partial differential equations

Discovering governing equations of a physical system, represented by partial differential equations (PDEs), from data is a central challenge in a variety of areas of science and engineering. Current methods require either some prior knowledge (e.g., candidate PDE terms) to discover the PDE form, or a large dataset to learn a surrogate model of the PDE solution operator. Here, we propose the first learning method that only needs one PDE solution, i.e., one-shot learning. We first decompose the entire computational domain into small domains, where we learn a local solution operator, and then find the coupled solution via a fixed-point iteration. We demonstrate the effectiveness of our method on different PDEs, and our method exhibits a strong generalization property

Bike Location and Road Obstacle Tracking Using Smart Helmet

In India, most of the people prefer two wheelers compared to other form of vehicle due to simplicity and low cost. One important problem is bike riders suffer from inadequate roads and bad driving conditions. Other important problem with biker is that most of the time they don?t like to wear helmet which could be fatal when accidents happen. Since in India the usage of two wheelers is more as compared to four wheelers, it requires more attention as far as safety is concerned. Motorcycles have high rate of fatal accidents than automobiles or trucks and buses. According to some statistics serious head injuries can happen even in low speeds. Ninety percent of head injury cases are due to road traffic accidents, about 72 percent are youngsters in the age group of 18 to 40. So to overcome this problem we have introduced a smart helmet with additional features like road hazard warning, bike authentication. In the previous research work that focuses on the point that the bike will not get start if the rider is not wearing helmet, so we modified this feature and make ones bike secure at crucial time especially when one is away from the bike and somebody is trying to steal it. So, we recapitulated the above features and introduce the project with some more unique characteristics. The main aim of this project is to introduce the smart interactive robotic helmet with features such as road obstacle identification, bike authentication, would help the rider in detecting important traffic sounds like fire siren or horn and the smart helmet would warn the rider when hazard is ahead. In this research work, the helmet is designed in such a way that it would provide more security to the rider hence the user is attracted towards the helmet because of its peculiar characteristics. If the rider runs on the bad intersection path, he could record for the present and upcoming road obstacle which is saved in mp3 format and can play that recording by pressing the button when he goes on same path again

Impact of photon addition and subtraction on nonclassical and phase properties of a displaced Fock state

Various nonclassical and quantum phase properties of photon added then subtracted displaced Fock state have been examined systematically and rigorously. Higher-order moments of the relevant bosonic operators are computed to test the nonclassicality of the state of interest, which reduces to various quantum states (having applications in quantum optics, metrology and information processing) in different limits ranging from the coherent (classical) state to the Fock (most nonclassical) states. The nonclassical features are discussed using Klyshko's, Vogel's, and Agarwal-Tara's criteria as well as the criteria of lower- and higher-order antibunching, sub-Poissonian photon statistics and squeezing. In addition, phase distribution function and quantum phase fluctuation have been studied. These properties are examined for various combinations of number of photon addition and/or subtraction and Fock parameter. The examination has revealed that photon addition generally improves nonclassicality, and this advantage enhances for the large (small) values of displacement parameter using photon subtraction (Fock parameter). The higher-order sub-Poissonian photon statistics is only observed for the odd orders. In general, higher-order nonclassicality criteria are found to detect nonclassicality even in the cases when corresponding lower-order criteria failed to do so. Photon subtraction is observed to induce squeezing, but only large number of photon addition can be used to probe squeezing for large values of displacement parameter. Further, photon subtraction is found to alter the phase properties more than photon addition, while Fock parameter has an opposite effect of the photon addition/subtraction. Finally, nonclassicality and non-Gaussianity is also established using $Q$ function.Comment: Nonclassical and quantum phase properties of photon added then subtracted displaced Fock state are studied in detai

Manipulating nonclassicality via quantum state engineering processes: Vacuum filtration and single photon addition

The effect of two quantum state engineering processes that can be used to burn hole at vacuum in the photon number distribution of quantum states of radiation field are compared using various witnesses of lower- and higher-order nonclassicality as well as a measure of nonclassicality. Specifically, the witnesses of nonclassical properties due to the effect of vacuum state filtration and a single photon addition on an even coherent state, binomial state and Kerr state are investigated using the criteria of lower- and higher-order antibunching, squeezing and sub-Poissonian photon statistics. Further, the amount of nonclassicality present in these engineered quantum states is quantified and analyzed by using an entanglement potential based on linear entropy. It is observed that all the quantum states studied here are highly nonclassical, and on many occasions the hole burning processes are found to introduce/enhance nonclassical features. However, it is not true in general. The investigation has further revealed that despite the fact that a hole at vacuum implies a maximally nonclassical state (as far as Lee's nonclassical depth is used as the quantitative measure of nonclassicality). However, any particular process of hole burning at vacuum does not ensure the existence of a particular nonclassical feature. Specifically,lower- and higher-order squeezing are not observed for photon added even coherent state and vacuum filtered even coherent state.Comment: Effect of holeburning is studied for various engineered quantum state