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dc.contributor.author
Stupar, Sandra
dc.contributor.supervisor
Renner, Renato
dc.contributor.supervisor
Short, Tony
dc.contributor.supervisor
Vedral, Vlatko
dc.date.accessioned
2019-02-25T13:15:39Z
dc.date.available
2019-02-25T12:33:59Z
dc.date.available
2019-02-25T13:15:39Z
dc.date.issued
2018
dc.identifier.uri
http://hdl.handle.net/20.500.11850/327503
dc.identifier.doi
10.3929/ethz-b-000327503
dc.description.abstract
Throughout the existence of humankind, people have organised their lives based on the sunrise and sunset, the Moon phases and star movements. Nature has guided our daily routines, as it still does, and it would be hard to imagine what life would look like without the already known cycles imposed by nature. As the humanity progressed, we have realised that a day is not always of the same length, but our sleep cycle most often is, and that it would be extremely useful to have further references for organising our day and habits. So people started calculating time with the Sun clock, sand clock, water clock etc. Since these were all limited in their performance, mechanical and pendulum clocks were introduced later, followed by quartz clocks, and as the ultimate performing ones, in the 20th century the first atomic clocks were constructed. This revolutionised time-keeping, speeded up technology development and made very precise coordination in every-day lives possible. It is now hard to think of spending a day without an accurate watch. But where does this notion of time and clocks physically arise from? And is it valid only in the classical limit that we experience, or is it possible to introduce very precise and well-synchronised quantum clocks as well? This is what we will try to deal with in this thesis. We start from the assumption that the only observable time is the one given by clocks, and hence to learn more about quantum time we need to build good quantum clocks and try to synchronise them. We define clocks as quantum systems that need to provide a time reference, such as a sequence of ticks. Further, we attempt to find limits on their synchronisation, since it is well known that quantum systems interact with their environment thereby getting disturbed. What we find out is that the performance of the quantum clocks we define depends crucially on their dimension (number of the distinguishable states available), and that the quantum clocks of a certain dimension could possibly perform better than the classical ones with the same state space size. The limitations to synchronising local quantum clocks suggest that global time in quantum mechanics might not be a physically grounded notion. We also investigate what limitations would be imposed on the evolution of our Universe, if it itself was/contained a quantum clock providing ticks that we observe as time. Our results show that the theory of inflation is consistent with the time keeping the Universe needed to perform at its early beginning, while the speed of evolution as of today would not be fast enough for the Universe to be able to store its ticks then. Although our argument is still not completely general, and does not exclude other possible theories for the evolution of the Universe, it is a novel approach to combining cosmology with quantum information and it would be very interesting to extend this research further.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
PHYSICS
en_US
dc.subject
QUANTENINFORMATION (INFORMATIONSTHEORIE)
en_US
dc.subject
Quantum information
en_US
dc.subject
Quantum information
en_US
dc.subject
QUANTUM THEORY
en_US
dc.title
Operational approach to time and clocks in quantum theory
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
dc.date.published
2019-02-25
ethz.size
122 p.
en_US
ethz.identifier.diss
25422
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02010 - Dep. Physik / Dep. of Physics::02511 - Institut für Theoretische Physik / Institute for Theoretical Physics::03781 - Renner, Renato / Renner, Renato
en_US
ethz.date.deposited
2019-02-25T12:34:01Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2019-02-25T13:15:46Z
ethz.rosetta.lastUpdated
2019-02-25T13:15:46Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
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