More information: Quantum dynamics of an electromagnetic mode that cannot contain N photons, Science (2015) 348:6236 776-779, doi:10.1126/science.1259345Related:1Phase space tweezers for tailoring cavity fields by quantum Zeno dynamics, Physical Review Letters (2010) 105:213601, doi:10.1103/PhysRevLett.105.2136012Dynamically protected cat-qubits: a new paradigm for universal quantum computation, New Journal of Physics (2014) 16:045014, doi:10.1088/1367-2630/16/4/045014 Journal information: Science , New Journal of Physics © 2015 Phys.org Squeezed quantum cats Huard addresses the implications of the finding stated in the paper that under a resonant drive, or cavity, the level occupation was found to oscillate in time, similarly to an N-level system. “By preventing any access to one energy level of the light mode, it indeed acts exactly as an N-level system – but here, since N can be chosen and modified in time, it’s as if we had engineered an atom with a spin (N-1)/2 that can change at will in time by simply turning on or off microwave signals. It would be interesting to observe the dynamics of such a spin whose number is changing in time.”Huard next discusses how fine control of the field in its phase space may enable applications in quantum information and metrology. “Our method is a new technique that can produce exotic quantum states of light similar to Schrödinger cat states or vacuum squeezed states that are well-suited for quantum information or metrology purposes by increasing the precision of field or position measurements.” (A vacuum squeezed state is a nonclassical state of light in which quantum noise is no longer independent of the phase of the light wave, and is below the standard quantum limit.) “Our method can also be used to generate and protect entanglement, which is a fundamental resource of quantum information, as well as to perform quantum error correction on qubits encoded using Schrödinger cat-like states.”In fact, the paper states that the new method allows the possibility of manipulating Schrödinger cat states in a unique way. “Our method is the essential brick that enables the creation of phase space light tweezers, as proposed by Jean-Michel Raimond and coworkers1,” Huard says. “These tweezers can displace parts of the Wigner function in its phase space one at a time.” (The Wigner function is a so-called quasiprobability distribution that links the Schrödinger wavefunction to a probability distribution in phase space, and counterintuitively can have regions of negative probability density.) “It therefore becomes possible to enlarge or rotate a Schrödinger cat state directly in its phase space.”This leads to the ability to effect quantum error correction of cat-qubits (quantum information encoded in logical bases composed of Schrödinger cat states) as a quantum computing paradigm. “In fact,” Huard points out, “a way to encode quantum information with superpositions of cat-like states was recently proposed in the context of circuit-QED by Mazyar Mirrahimi and coworkers2,” adding that finding ways to perform quantum error correction on these states is essential for their potential use in a quantum computing architecture. “We believe that our technique could be used to perform this quantum error correction in a unique way. Indeed, decoherence leads to an exponential relaxation of the cat size, which needs to be overcome – and by displacing the cat ‘legs’ one by one using QZD, this relaxation can be canceled without losing any quantum information.”Looking ahead, Huard tells Phys.org that the researchers are “pursuing the investigation of the fascinating effect of measurement on quantum systems. For instance,” he illustrates, “we now have an experiment where we intercept the signal that leaks towards the environment of a qubit and usually leads to decoherence. However, using this signal we can now infer what the environment knows about the qubit state and preserve the purity of the quantum state – and we’ve recently managed to use that signal for preserving any state by feedback.” In addition, he adds, they are interested in applying their technique to systems with longer coherence times and to Schrödinger cat preservations.Regarding other areas of research that might benefit from their study, Huard concludes that “it’s hard to tell right now – but in the long run, if our technique helps build quantum simulators or computers, it could have an impact in many areas requiring intense computation, such as machine learning or chemistry.” Explore further (Phys.org)—Constructing quantum computers and other quantum devices requires the ability to leverage quantum properties such as superposition and entanglement – but these effects are fragile and therefore hard to maintain. Recently, scientists at Ecole Normale Supérieure in Paris demonstrated a novel method for controlling the quantum properties of light by probing a superconducting circuit in a cavity with microwave photons to control the energy levels that photon quanta can occupy. Specifically, the scientists prevented access to a single energy level corresponding to a number of photons N, and thereby confined the dynamics of the field to levels 0 to N -1. In so doing, the intracavity field changed from a classical wave to a Schrödinger cat of light – a superposition between two waves of opposite phases instead of a single one. As a result, this new technique could apply to the development of quantum computers by protecting qubits from decoherence as well as enhancing quantum error correction and quantum systems measurement. Prof. Benjamin Huard discussed the paper that he and his colleagues published in Science. “The primary difficulty in developing our method for manipulating electromagnetic modes by effectively controlling their phase space was to find a proper way of preventing any access to one or few energy levels,” Huard tells Phys.org. “We did that using another quantum system – a superconducting qubit – which allowed us to change the energy of any level we chose by simply turning a microwave signal on or off. In this context, the main challenge was designing a cavity and a qubit with the right properties to realize and observe this new method of control.”The scientists also had an issue in finding that level occupation oscillated in time when using the same light mode and qubit for several operations. “The basic experiment consists in driving the light mode while the qubit controls its phase space,” Huard explains. “However, in order to measure the level occupation in time, we had to use the same qubit as a photocounter, and the same light mode to measure the qubit state.” (Photocounters tally photon distributions by counting photoelectric electrons, or photoelectrons – that is, electrons emitted by various metals when illuminated by photons.)A third obstacle was using circuit quantum electrodynamics, or circuit-QED, architecture – the implementation of quantum electrodynamics (a quantum field theory of electromagnetic force) for circuits – to apply quantum Zeno dynamics (QZD) to light. QZD is based on the quantum Zeno effect (QZE) – named after the Zeno arrow paradox – in which if observed continuously an unstable particle will never decay, meaning that an unstable quantum system measured with sufficient frequency will not evolve. However, in certain circumstances, quantum Zeno dynamics – in which the quantum system changes over time – can occur. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. , Physical Review Letters Citation: Training Schrodinger’s cat: Controlling the quantum properties of light (2015, July 8) retrieved 18 August 2019 from https://phys.org/news/2015-07-schrodinger-cat-quantum-properties.html Classical vs. Schrödinger cats. The top figure represents the classical field inside of a cavity which is illuminated by a microwave-generated tone. The phase is well-defined (green corresponds to fields with the original phase, to which a living cat corresponds) and the amplitude increases linearly. The bottom figure represents the experimental results, in which three photons are forbidden in the cavity. In that case, at some time the field amplitude saturates and it enters in a quantum superposition of two possible phases (the original in green and its opposite in red). After this intermediate interval, the amplitude decreases, thereby keeping the opposite phase until it returns to zero amplitude. By analogy, one can say that the intermediate regime corresponds to a superposition of two classical states with opposite phases, very much like a superposition of a dead and living cat. Credit: Benjamin Huard. Zeno cat. A Zeno cat refers to non-classical states of light created by shining a cavity on resonance while it is forbidden to access a given energy level. The name originates from the Zeno effect, which can similarly prevent an energy level from being occupied by the sole fact of measuring its occupation frequently. The cat comes from the similarity of such a state with a Schrödinger cat state of light: a superposition between two classical states of light. The Zeno cat figure corresponds to the study’s experimental design. Credit: Benjamin Huard. “With its large number of energy levels and ease of control,” Huard points out, “a single electromagnetic mode offers a wider and more controllable phase space than atoms and two-level systems. Nevertheless, in order to make it work, we had to identify the several constraints on the parameters we had access to. Using superconducting circuits helped since it is fairly easy to tune their parameters and establish coupling to microwave light. Using the same systems twice for various operations required many careful calibrations, and we had to find the optimal temporal sequences to realize the experiment.”
The CBI on Tuesday told a special court that graft charges should be maintained against two government officials, facing prosecution in a coal scam case in which the Delhi High Court had quashed charges against Chhattisgarh- based Prakash Industries Ltd (PIL) and its director.Special Public Prosecutor R S Cheema and CBI prosecutor V K Sharma filed the agency’s reply to the plea of accused Goutam Kumar Basak and Soumen Chatterjee seeking alteration of charges framed against them. Also Read – Need to understand why law graduate’s natural choice is not legal profession: CJICBI, in its reply filed before special CBI judge Bharat Parashar, said the charge of public servants abusing official position under the Prevention of Corruption Act should be maintained against the two accused persons.The prosecutor, however, said the charge of criminal conspiracy under the IPC should be recast.The counsel for Basak and Chatterjee sought time to go through the agency’s reply and to argue in the matter.The court granted time to the defence counsel and fixed the case for arguments on the application on 8 December.
Depression combined with obesity, high blood pressure and unhealthy cholesterol levels may significantly increase the risk of developing type 2 diabetes, finds a new study.The findings showed that people who suffer with depression and metabolic risk factors such as obesity, high blood pressure and unhealthy cholesterol levels are more than six times more likely to develop type 2 diabetes.People with depression, alone, were not significantly at greater risk of developing type 2 diabetes. But people only with metabolic risk factors like obesity, high blood pressure and unhealthy cholesterol levels and not depression were around four times more likely to develop type 2 diabetes. Also Read – ‘Playing Jojo was emotionally exhausting’“Emerging evidence suggests that not depression, per se, but depression in combination with behavioural and metabolic risk factors increases the risk of developing type 2 diabetes and cardiovascular conditions,” said lead author Norbert Schmitz, associate professor in McGill University in Canada.The results, published in the journal Molecular Psychiatry, suggested that when depression combines with metabolic risk factors, the risk of developing diabetes rises to a level beyond the sum of its parts. For the study, the researchers analysed 2,525 participants who were aged between 40 and 69 for four-and-a-half year.
The findings showed that the exhaustion levels were greater in employees with high “pro-social motivation” – or those who care deeply about the welfare of others. “Helping co-workers can be draining for the helpers, especially for employees who help a lot,” said Russell Johnson, Associate Professor at Michigan State University in the US.“When the high pro-social motivation people are asked for help, they feel a strong obligation to provide help, which can be especially taxing,” he added. Also Read – ‘Playing Jojo was emotionally exhausting’For the study, the team conducted a survey on 68 employees across various industries, including finance, engineering and health care, for 15 consecutive workdays.“On days when employees find themselves engaging in unusually high amounts of helping, they can attempt to bolster their energy by the strategic use of breaks, naps and stimulants like caffeine,” the researchers suggested. Help-seekers, on the other hand, should realise that asking for help, especially multiples times a day, has detrimental effects on the employees who are helping, the researchers said.
Kolkata: An elderly woman was allegedly beaten up by her son and daughter-in-law on Wednesday night. When one of her relatives came to the rescue, he was also thrashed. On Thursday morning, police arrested both the accused. According to locals, Reba Mondal, a resident of Sindrani Haringarh at Bagda lost her husband Atul Mondal about two years ago. Since then Reba’s son Ashok and daughter-in-law Rita used to torture her for property. As the days passed, the intensity of torture went higher. To escape from the endless torture, Reba went to her daughters Suparna Silinda and Aparna Biswas to seek shelter. Around four months ago, Reba fell sick. When her daughters informed Ashok, he took Reba and left her at a hospital. Also Read – Rain batters Kolkata, cripples normal lifeThe daughters found out that Ashok had left her at a hospital and did not turn up again. After Reba got discharged, she went to her daughter’s place to stay. However, on Wednesday, she wished to return to her own house. Ashok and Rita became furious on seeing her and beat up Reba in front of their neighbours. When Reba’s brother-in-law Bibhas Mondal tried to save her, he also beaten up by the duo. Reba was seriously injured. Locals somehow managed to recover Reba and Bibhas from the clutches of Ashok and Rita. Later, both of them were admitted to Bagda Rural Hospital. On Thursday, police were informed by some locals about the incident and went to meet Reba at the hospital. As per her statement, police immediately initiated a case against Ashok and Rita and soon both of them were arrested on charges of beating Reba and Bibhas.
Learning foreign languages enhances our brain’s elasticity and its ability to code information, a study has found. The study mentions that the more foreign languages one learns, the more effectively brain reacts and processes the data accumulated in the course of learning. Researchers carried out experiments among 22 students (10 male and 12 female) where the brain’s electrical activity was measured with EEG (electroencephalography). The subjects had electrodes placed on their heads and then listened to recordings of different words in their native language, as well in foreign languages. When the known or unknown words popped up, changes in the brain’s activity were tracked and the researchers especially focused on the speed at which the brain readjusted its activity to treat unknown words. The experiment showed that the brain’s electrical activity of those participants who had already known some foreign languages, was higher. Also Read – Add new books to your shelf“The more languages someone mastered, the faster the neuron network coding the information on the new words was formed. Consequently, this new data stimulates the brain’s physiology — loading the mind with more knowledge boosts its elasticity,” said Yuriy Shtyrov, researcher at the University of Helsinki in the study published in the journal Scientific Reports. “When we achieve better insight into the principles of creating and strengthening neuron networks, we will be able to harness these mechanisms, speed them up and improve the learning process,” Shtyrov added.
Mothers who leave work to raise children often sacrifice more than the pay for their time off as when they come back their wages reflect lost raises, researchers said. Researchers from New York University in the US examined data from a survey that tracked 4,658 women from 1976, when they were 14- to 21-year-olds, to 2010, when they were largely past their child rearing years at ages 45 to 52.“In the case of highly skilled white women with high wages, what is striking is that they have the highest penalties despite the fact that they have the most continuous work experience of any group of women, which, other things being equal, would reduce their penalties,” said Paula England, professor at New York University. Also Read – Add new books to your shelf“Their high returns to experience and tenure mean that loss of every year of work caused by motherhood is much more costly for their future wages, even in proportionate terms, than it is for other groups of women,” said England.England studied how motherhood penalised white and black women and how this varied by their skill and wage level. She found that highly skilled, highly paid white women lose an average of 10 per cent in their wage per child. However, those with lower skills and/or lower wages lose significantly less, between four and seven per cent of their wage per child. Also Read – Over 2 hours screen time daily will make your kids impulsiveThe penalties were lower for black women than for white women; however, unlike the white women, the penalties for black women did not differ significantly by skill or wage, said England. “Women with the highest total motherhood penalties are in an advantaged group with high skills and high wages; even after they become mothers and suffer the steepest penalty, they are typically affluent because their own earnings are still relatively high, and many of them are married to high-earning men,” said England. “Given their relative privilege, we might still want to give priority to policies, such as child care subsidies, that help low-income women,” she said. “However, in an era when there are still few women CEOs and we have yet to elect a woman president, it is important to understand how much motherhood affects the careers of women at the top and to consider how this can be changed,” she said.The study was published in the journal American Sociological Review.
Kolkata: Mayor Firhad Hakim, who is also in charge of the state Urban Development and Municipal Affairs department, will send a proposal to the state government to designate Kolkata Municipal Corporation (KMC) for maintenance of all city roads and Kolkata Metropolitan Development Authority (KMDA) for maintenance of all city bridges and flyovers.The proposal will also contain the appeal to designate the state Public Works Department (PWD) to carry out maintenance of bridges and flyovers in the districts. Also Read – Rain batters Kolkata, cripples normal life”In recent times there have been issues, particularly over maintenance of roads and flyovers in the city and passing over responsibility to one another. If the entire maintenance work is done by KMC for roads and KMDA for the flyovers, then work can be done quickly and in a smoother way. So we will be sending a proposal to the government,” Hakim said after attending a high level meeting at the KMC headquarters with officials from KMDA, PWD, Housing & Infrastructure Development Corporation (HIDCO), West Bengal Pollution Control Board etc. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedHowever, KMC or KMDA will collect maintenance charge from the respective agencies which own different roads or flyovers. It may be mentioned that during the monsoon season this year, when the roads in the city had developed potholes at a number of places, Chief Minister Mamata Banerjee had instructed KMC to carry out road repair and later charge fees from the agencies. Apart from KMC, there are roads in the city that are maintained by the state PWD, state Irrigation department, KMDA, HRBC etc. Kolkata Port Trust is also responsible for road maintenance in a large part of the Port area.