COOKIES: By using this website you agree that we can place Google Analytics Cookies on your device for performance monitoring. |

University of Cambridge > Talks.cam > CQIF Seminar > Leggett Garg Inequalities: a Quasi-probability Approach to No-Signalling in Time and New Measurement Protocols

## Leggett Garg Inequalities: a Quasi-probability Approach to No-Signalling in Time and New Measurement ProtocolsAdd to your list(s) Download to your calendar using vCal - Jonathan Halliwell, Imperial
- Thursday 26 January 2017, 14:15-15:15
- MR4, Centre for Mathematical Sciences, Wilberforce Road, Cambridge.
If you have a question about this talk, please contact Steve Brierley. The Leggett-Garg (LG) inequalities were proposed in order to assess whether sets of pairs of sequential measurements on a single quantum system can be consistent with an underlying notion of macroscopic realism (MR) at three, four or more times. I review the LG formalism and note that the LG inequalities alone are a necessary condition for MR, but not a sufficient one, the shortfall lying in the description of the system at two times, the key point at which LG systems differ from the analogous CHSH inequalities for an EPRB pair. I argue that this shortfall can be addressed by describing the two-time measurement situation in terms of a simple, measurable quasi-probability, which provides a measure of macrorealism at two times. It is closely related to the no-signalling in time condition of Kofler and Brukner. This measure, when combined with the LG inequalities, provides a characterization of macrorealism more detailed than that provided by the LG inequalities alone. In particular, when the quasi-probability is non-negative, the LG system has a natural parallel with the EPRB system and Fine’s theorem, and this augmented LG system is then both a necessary and sufficient condition for macrorealism. In all experiments measuring such systems, the measurements have to be carried out non-invasively in order to evade alternative classical explanations. Two simple protocols are proposed to achieve this. The Leggett-Garg Inequalities and No-Signalling in Time: A Quasi-Probability Approach. J. J. Halliwell Phys. Rev. A 93 , 022123 (2016) Decoherent Histories and Measurement of Temporal Correlation Functions for Leggett-Garg Inequalities. J.J.Halliwell Phys. Rev. A 94 , 052131 (2016) Leggett-Garg Correlation Functions from Non-Invasive Velocity Measurement Continuous in Time. J.J. Halliwell Phys. Rev. A 94 , 052114 (2016) This talk is part of the CQIF Seminar series. ## This talk is included in these lists:- All CMS events
- CMS Events
- CQIF Seminar
- DAMTP info aggregator
- MR4, Centre for Mathematical Sciences, Wilberforce Road, Cambridge
- bld31
Note that ex-directory lists are not shown. |
## Other listsAPDE Seminars on Adaptation to Climate Change Non-Covalent Chemistry Symposium## Other talksPoison trials, panaceas and proof: debates about testing and testimony in early modern European medicine “It’s like they’re speaking a different language!” Investigating an accidental resistance to school mathematics reform Internal Displacement in Cyprus and childhood: The view from genetic social psychology Sir Richard Stone Annual Lecture: The Emergence of Weak, Despotic and Inclusive States Electoral intrigue, ethnic politics and the vibrancy of the Kenyan public sphere Optimising the definition of MR-based lung imaging biomarkers |