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Quantum Information

  1. Feb 19, 2014 #1
    Hi guys, i've been reading a paper recently about trapping pseudo molecules in a magnetic field gradient. It says at one point that one of the successes has been due to using microwaves opposed to lasers; they claim that the reason for this is because lasers are notoriously difficult for maintaining frequency stability. My question is then why are Mazers easier to keep stable?

    Thanks in advance.
     
  2. jcsd
  3. Feb 19, 2014 #2

    ZapperZ

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    You must make a proper citation of the source! While this forum may appear to be any ordinary, public forum, we are trying to instill the habit of always citing the source of what we read, heard, etc. So please cite it as if you are making a citation in a science paper (author/s, publication, volume, page, year).

    https://www.physicsforums.com/blog.php?b=2703 [Broken]

    Zz.
     
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  4. Feb 19, 2014 #3
    Apologies, the following is the paper i was reading;

    Designer Spin Pseudomolecule Implemented with Trapped Ions in a Magnetic Gradient
    A. Khromova, Ch. Piltz, B. Scharfenberger, T. F. Gloger, M. Johanning, A. F. Varo ́ n, and Ch. Wunderlich* Department Physik, Naturwissenschaftlich-Technische Fakulta ̈t, Universita ̈t Siegen, 57068 Siegen, Germany
    (Received 3 February 2012; published 1 June 2012)
     
  5. Feb 19, 2014 #4

    ZapperZ

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    What journal was this published in?

    Zz.
     
  6. Feb 19, 2014 #5
    PHYSICAL REVIEW LETTERS

    DOI: 10.1103/PhysRevLett.108.220502.

    Thanks.
     
  7. Feb 19, 2014 #6

    f95toli

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    I had a quick look at the paper, and I can't see where they explicity state that masers are more stable; as far as I can tell they do not even mention masers,
    They do say that lasers are more difficult to work with, but that is a separate issue.

    It is true that stabilising lasers is far from trivial, but on the other hand they operate at very high frequencies. Hence, the relatively stability is often extremely good. By using a frequency comb it is also possible to lock a laser to a maser.

    Also, the word stability does not mean anything unless you also give a timescale. Hydrogen masers are some of the most stable references we have for short timescales (which is why they are used to generate the timesignal), but they do not work well for longer timescales (which is where atomic clocks work well). Hence, for e.g. keepting track of time we use both masers and atomic clocks (Cs fountains).
     
  8. Feb 19, 2014 #7
    Thanks a lot for the response. The paper talks about radiating the ions with microwaves, thus i assumed this would be with a mazer.
     
  9. Feb 20, 2014 #8
    You actually don't necessarily need a maser for that. Using microwaves for quantum information is also done in other approaches, for example with superconducting qubits and in combination with lasers in NV-centers. The good thing about microwave is as you stated in the OP that they are much easier to get stable, and that's because simple (though well made) electronic circuits (antennas) can be enough, as long as they are situated close enough to you sample, which are much easier to deal with than lasers.

    Also, about the stablilty, what matters for quantum information is usually the short term stability, i.e. you have to remain coherent with your system between pulses/gate operations, and it's much easier to achieve a stable system in the GHz time scale as opposed to the hundreds of THz optical regime. The drawbacks of the microwave regime on the other hand include that it's hard to achieve good focusing and that it doesn't interact well with certain other techniques like coupling to fiber communication, which may be required for some applications.
     
  10. Feb 20, 2014 #9

    f95toli

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    Masers are hardly ever used for "radiating" anything. The primary applications of masers are as frequency standards and amplifiers.
    For the type of experiment they describe in the paper you can just use normal microwave sources, the technology is more or less the same as what is used to generate the microwaves in your mobile phone or WIFI router.
     
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