Posted on 01/25/2019 1:01:21 PM PST by ETL
An old thought experiment now appears in a new light. In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. A group of researchers led by Gerhard Rempe, Director of the Department of Quantum Dynamics at the Max Planck Institute of Quantum Optics, has now realized an optical version of Schrödinger's thought experiment in the laboratory. In this instance, pulses of laser light play the role of the cat. The insights gained from the project open up new prospects for enhanced control of optical states, that can in the future be used for quantum communications.
"According to Schrödinger's idea, it is possible for a microscopic particle, such as a single atom, to exist in two different states at once. This is called a superposition. Moreover, when such a particle interacts with a macroscopic object, they can become 'entangled', and the macroscopic object may end up in superposition state. Schrödinger proposed the example of a cat, which can be both dead and alive, depending on whether or not a radioactive atom has decayed a notion which is in obvious conflict with our everyday experience," Professor Rempe explains.
In order to realize this philosophical gedanken experiment in the laboratory, physicists have turned to various model systems. The one implemented in this instance follows a scheme proposed by the theoreticians Wang and Duan in 2005. Here, the superposition of two states of an optical pulse serves as the cat. The experimental techniques required to implement this proposal in particular an optical resonator have been developed in Rempe's group over the past few years.
A test for the scope of quantum mechanics
The researchers involved in the project were initially skeptical as to whether it would be possible to generate and reliably detect such quantum mechanically entangled cat states with the available technology. The major difficulty lay in the need to minimize optical losses in their experiment. Once this was achieved, all measurements were found to confirm Schrödinger's prediction. The experiment allows the scientists to explore the scope of application of quantum mechanics and to develop new techniques for quantum communication.
The laboratory at the Max Planck Institute in Garching is equipped with all the tools necessary to perform state-of-the-art experiments in quantum optics. A vacuum chamber and high-precision lasers are used to isolate a single atom and manipulate its state. At the core of the set-up is an optical resonator, consisting of two mirrors separated by a slit only 0.5 mm wide, where an atom can be trapped. A laser pulse is fed into the resonator and reflected, and thereby interacts with the atom. As a result, the reflected light gets entangled with the atom. By performing a suitable measurement on the atom, the optical pulse can be prepared in a superposition state, just like that of Schrödinger's cat. One special feature of the experiment is that the entangled states can be generated deterministically. In other words, a cat state is produced in every trial.
"We have succeeded in generating flying optical cat states, and demonstrated that they behave in accordance with the predictions of quantum mechanics. These findings prove that our method for creating cat states works, and allowed us to explore the essential parameters," says Ph.D. student Stephan Welte.
A whole zoo of states for future quantum communication
"In our experimental setup, we have succeeded not only in creating one specific cat state, but arbitrarily many such states with different superposition phases a whole zoo, so to speak. This capability could in the future be utilized to encode quantum information," adds Bastian Hacker.
"Schrödinger's cat was originally enclosed in a box to avoid any interaction with the environment. Our optical cat states are not enclosed in a box. They propagate freely in space. Yet they remain isolated from the environment and retain their properties over long distances. In the future we could use this technology to construct quantum networks, in which flying optical cat states transmit information," says Gerhard Rempe. This underlines the significance of his group's latest achievement.
Explore further: Proposed test of quantum superposition measures 'quantum revivals'
More information: Bastian Hacker et al. Deterministic creation of entangled atomlight Schrödinger-cat states, Nature Photonics (2019). DOI: 10.1038/s41566-018-0339-5
Journal reference: Nature Photonics
Provided by: Max Planck Society
First something has to create a photon of light. I’m curious what gets it to suddenly travel at the speed of light, in all directions.
You need to read a bit more about quantum theory.
Objects big enough to see (like cats) are indeed either dead or alive. But-- at least according to quantum theory-- at a subatomic level, minuscule particles are simultaneously in two places at once. It's not just that we can't tell if they are in one place or another; they are literally in both places at the same time.
Schrodinger's "thought experiment" was an attempt to ridicule this theory, but so far, evidence has tended to support the quantum theory.
The speed of light is the supposed speed limit of the universe. It isn't only light that travels at that speed, but, according to theory, any massless object. ie, gravitons, alleged carrier of the gravitational "force".
all measurements were found to confirm Schrödinger’s prediction.
Schrödingers prediction was that the cat would be both dead and alive at the same time. How did they measure that?
Experiments like these leave me skeptical. They make sweeping claims but were just expected to take their word for it that the experiment shows what they claim.
The prediction of quantum theory (not Schrodinger's prediction) was that a single atom could exist in two mutually-exclusive states at once. The experimenters claim to have achieved that result; I don't know nearly enough physics to comment on whether they did or not.
The cat thing was just a joke on Schrodinger's part. He did not believe that quantum theory was correct and, to illustrate its absurdity, he imagined a giant Rube Goldberg-like machine which could kill a cat powered by a single atom (an engineering impossibility, of course) and said that if quantum theory were correct, the cat would be simultaneously dead and alive.
The reason quantum entanglement, it is real, is still a debate is we do not understand it. I doubt we will in my lifetime.
Schroeder’s cat is alive and well in his box. If you open it he may die, even worse he may be alive and entanglement goes out the window.
I wish Schroeder had selected Chihuahuas for possible quantum extinction. I like my cats, I like my dogs but abhor Chihuahuas.
I think its all showmanship. Their experiment does not come close to approximating what Schrödinger predicted based on quantum theory. Schrödinger was dealing with cats not atoms. Also whether an atom exists in two states simultaneously is not in theory determinable by a measurement since the probability distribution collapses into one state or the other when the measurement is made. These articles tend to be sensationalism and little more. They are far too obscure to offer any real insight.
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