Your source for the latest research news

Wednesday, 4 March 2020

Physicists film the quantum transition of an atom



Measuring a quantum system causes it to change -- one of the strange but fundamental aspects of quantum mechanics. Researchers have now been able to demonstrate how this change happens.

Quantum physics describes the inner world of individual atoms, a world very different from our everyday experience. One of the many strange yet fundamental aspects of quantum mechanics is the role of the observer – measuring the state of a quantum system causes it to change.

Despite the importance of the measurement process within the theory, it still holds unanswered questions: Does a quantum state collapse instantly during a measurement? If not, how much time does the measurement process take and what is the quantum state of the system at any intermediate step?

A collaboration of researchers from Sweden, Germany and Spain has answered these questions using a single atom – a strontium ion trapped in an electric field. The measurement on the ion lasts only a millionth of a second. By producing a “film” consisting of pictures taken at different times of the measurement they showed that the change of the state happens gradually under the measurement influence.



Superposition preserved

Atoms follow the laws of quantum mechanics which often contradict our normal expectations. The internal quantum state of an atom is formed by the state of the electrons circling around the atomic core. The electron can circle around the core in an orbit close or further away. Quantum mechanics, however, also allows so called superposition states, where the electron occupies both orbits at once, but each orbit only with some probability.

The result of the experiment can be summarized in an animated GIF that shows what happens to the quantum state of the ion during that millionth of a second. The state can be visualized using a three-dimensional board. The heights of the bars indicate the degree of superposition of the possible quantum states. The film shows how during the measurement some of the superpositions are lost – and how this loss is gradual – while others are preserved as they should be in an ideal quantum measurement. Source: F. Pokorny et al., "Tracking the dynamics of an ideal quantum measurement", Physical Review Letters 2020.


“Every time when we measure the orbit of the electron, the answer of the measurement will be that the electron was either in a lower or higher orbit, never something in between. This is true even when the initial quantum state was a superposition of both possibilities. The measurement in a sense forces the electron to decide in which of the two states it is”, says Fabian Pokorny, researcher at the Department of Physics, Stockholm University.

The “film” displays the evolution during the measurement process. The individual pictures show tomography data where the height of the bars reveal the degree of superposition that is still preserved. During the measurement some of the superpositions are lost – and this loss happens gradually – while others are preserved as they should be for an ideal quantum measurement.

Important for quantum computers

“These findings shed new light onto the inner workings of nature and are consistent with the predictions of modern quantum physics”, says Markus Hennrich, group leader of the team in Stockholm.

These results are also important beyond fundamental quantum theory. Quantum measurement are an essential part of quantum computers. The group at Stockholm University is working on computers based on trapped ions, where the measurements are used to read out the result at the end of a quantum calculation.




Bibliography:

Tracking the Dynamics of an Ideal Quantum Measurement

Fabian Pokorny, Chi Zhang, Gerard Higgins, Adán Cabello, Matthias Kleinmann, Markus Hennrich.

Physical Review Letters, 2020;

DOI: 10.1103/PhysRevLett.124.080401

2 comments:

  1. Cure for Herpes Virus
    Its a great pleasure for me to write this testimony about how I got my Genital Herpes cured within a month. I have been reading so many comments of some people who were cured from various diseases by Dr Ahmed Usman herbal medicine but I never believed them. I was hurt and depressed so I was too curious and wanted to try DR. Ahmed then i contacted him through his email, he assured me 100% that he will cure me, I pleaded with him to help me out. My experience with him was great. He sent me his herbal medicine and prescribed the usage of the herbal medicine. He asked me to go for a medical check up after two weeks of usage. I agreed with him I took this herbal medicine as instructed by him and went for a check up, to my greatest surprise my result was negative, I am really happy that I am cured and healthy again. I have waited for a month to be very sure I was completely cured before writing this testimony. I did another blood test one week ago and it was still Herpes negative, with no trace of the virus on my blood so I guess its time I recommend him to anyone suffering from Herpes Virus. contact Dr. Ahmed through his official email address: drahmedusman5104@gmail.com  
    He has herbal cure for Diabetes, Hepatitis, Cancer, Heart diseases and Liver diseases. 

    ReplyDelete
  2. I am here to give my testimony about chief dr lucky who helped me in my life, i want to inform the public how i was cured from herpes simplex virus by chief dr lucky, i visited different hospital but they gave me list of drugs like Famvir, Zovirax, and Valtrex which is very expensive to treat the symptoms and never cured me. I was browsing through the Internet searching for remedy on herpes and i saw comment of people talking about how chief dr lucky cured them. when i contacted him he gave me hope and send a Herbal medicine to me that i took and it seriously worked for me, am a free person now without problem, my herpes result came out negative. I pray for you chief dr lucky am cured you can also get your self cured my friends if you really need my doctor help, you can reach him now.
    Email: chiefdrlucky@gmail.com  Call or What's App +2348132777335  
    Website :  http://chiefdrluckysolutionhome.website2.me/ 

    ReplyDelete