Experimental Quantum Foundations

Conference Date: 
Friday, September 23, 2016 (All day)
Scientific Areas: 
Quantum Foundations

 

Our understanding of the ways in which quantum theory represents a conceptual innovation relative to classical physics---and of the experimental signatures of such nonclassicality---continues to improve. Simultaneously, the number of quantum systems over which we have fine experimental control is growing. As a result, experiments addressing issues in quantum foundations are flourishing. This workshop aims to explore some recent work in this young field and to consider new directions.

  • Jeff Lundeen, University of Ottawa
  • Jean-Phillipe MacLean, Institute for Quantum Computing
  • Michael Mazurek, University of Waterloo
  • Lorenzo Procopio, University of Vienna
  • Matthew Pusey, Perimeter Institute
  • Robert Spekkens, Perimeter Institute
  • Aephraim Steinberg, University of Toronto
  • Jeremy Bejanin, University of Waterloo
  • Daniel Brod, Perimeter Institute
  • Aharon Brodutch, University of Toronto
  • Matthew Brown, University of Waterloo
  • John Donohue, University of Waterloo
  • Dorren Fraser, Univeristy of Waterloo
  • Lucien Hardy, Perimeter Institute
  • Lauren Hayward Sierens, Perimeter Institute
  • Sara Hosseini, Australian National University
  • Hemant Katiyar, University of Waterloo
  • Na Young Kim, University of Waterloo
  • Bohdan Kulchytskyy, University of Waterloo
  • Ravi Kunjwal, Perimeter Institute
  • Sangil Kwon, Institute for Quantum Computing
  • Jeff Lundeen, University of Ottawa
  • Jean-Phillipe MacLean, Institute for Quantum Computing
  • Michael Mazurek, University of Waterloo
  • Markus Mueller, Perimeter Institute & University of Western Ontario
  • Krishnamohan Parattu, Perimeter Institute
  • Lorenzo Procopio, University of Vienna
  • Matthew Pusey, Perimeter Institute
  • Kevin Resch, University of Waterloo
  • Jeff Salvail, University of Waterloo
  • David Schmid, Perimeter Institute
  • Behrooz Semnani, University of Waterloo
  • Robert Spekkens, Perimeter Institute
  • Aephraim Steinberg, University of Toronto
  • Sai Sreesh Venuturumilli, University of Waterloo

Friday, September 23, 2016

Time

Event

Location

9:25 - 9:30 am Welcome Alice Room

9:30 – 10:30am

Michael Mazurek, University of Waterloo &
Matthew Pusey, Perimeter Institute
Direct experimental reconstruction of the Bloch sphere

Alice Room

10:30 – 11:00am

Coffee Break

Bistro – 1st Floor

11:00 – 12:00pm

Lorenzo Procopio, University of Vienna
Single-photon test of Hyper-Complex Quantum Theories

Alice Room

12:00 - 1:00pm

Aephraim Steinberg, University of Toronto
Experimental measurement tradeoffs, from Heisenberg to Aharonov to quantum data compression

Alice Room

1:00 – 2:30pm

Lunch

Bistro – 2nd Floor

2:30 – 3:30pm

Jeff Lundeen, University of Ottawa
Naïve experiments for measuring incompatible observables

Alice Room

3:30 – 4:00pm

Coffee Break

Bistro – 1st Floor

4:00 – 5:00pm

Jean-Phillipe MacLean, Institute for Quantum Computing &
Robert Spekkens, Perimeter Institute
Experimental implementation of quantum-coherent mixtures of causal relations

Alice Room

 

Jeff Lundeen, University of Ottawa

Naïve experiments for measuring incompatible observables

Sets or pairs of incompatible observables, such as momentum and position, play a pivotal role in a wide range of distinctly quantum effects and applications, including quantum cryptography, the Heisenberg Uncertainty Principle, quantum state tomography, and Bell’s inequalities. In particular, in quantum physics, we are prohibited from precisely measuring the values of incompatible observables, a fact that is at the heart of the nature of the quantum state. In this talk, I will explore an assortment of strategies that simple-mindedly attempt to circumvent this prohibition. Motivated by these naïve strategies, we experimentally investigate the use of weak measurement and optimal quantum cloning to perform joint measurements on photons. The direct outcome of these measurements are, depending on the strategy, the wavefunction, the Dirac distribution, and the density matrix of the measured quantum system. Consequently, these naïve strategies provide new ways to characterize quantum systems and to understand the very entities that we are measuring, such as the wavefunction.

Jean-Phillipe MacLean, Institute for Quantum Computing &
Robert Spekkens, Perimeter Institute

Experimental implementation of quantum-coherent mixtures of causal relations

Understanding the causal influences that hold among the parts of a system is critical both to explaining that system's natural behaviour and to controlling it through targeted interventions. In a quantum world, understanding causal relations is equally important, but the set of possibilities is far richer. The two basic ways in which a pair of time-ordered quantum systems may be causally related are by a cause-effect mechanism or by a common cause acting on both. Here, we show that it is possible to have a coherent mixture of these two possibilities. We realize such a nonclassical causal relation in a quantum optics experiment and derive a set of criteria for witnessing the coherence based on a quantum version of Berkson's paradox. (Joint work with Katja Ried and Kevin Resch)

Michael Mazurek, University of Waterloo &
Matthew Pusey, Perimeter Institute

Direct experimental reconstruction of the Bloch sphere

The scientific journey from the first hints of quantum behaviour to the Bloch sphere in your textbook was a long and tortuous one. But using some of the technological and conceptual fruits of that journey, we show that an experiment can manifest the Bloch sphere via an analysis that doesn't require any quantum theory at all. Our technique is to fit experimental data to a generalised probabilistic theory, which allows us to infer both the dimension and shape of the state and measurement spaces of the system under study. We test our technique on an experiment measuring a variety of single-photon polarization states. As expected, the reconstructed state space closely resembles the Bloch sphere, and we are able to place small upper bounds on how much the true theory describing our experiment could possibly deviate from quantum mechanics.

Lorenzo Procopio, University of Vienna

Single-photon test of Hyper-Complex Quantum Theories

One of the most successful theories in physics until now is quantum mechanics. However, the physical origins of its mathematical structure are still under debate, and a "generalized" quantum theory to unify quantum mechanics and gravity is still missing. Recently, in an effort to better understand the mathematical structure of quantum mechanics, theories containing the essence of quantum mechanics, while also having a broader description of physical phenomena, have been proposed. These so-called "post-quantum theories" have only been recently tested at the lab. In this talk, I will present the results of our experimental test using single photons to probe one of these post-quantum theories; namely, hyper-complex quantum theories. Interestingly, in hyper-complex theories simple phases do not necessarily commute. To study this effect, we apply two physically different optical phases, one with a positive and one with a negative refractive index, to single photons inside of a Sagnac interferometer.  Through our measurements we are able put bounds on this particular prediction of hyper-complex quantum theories.

Aephraim Steinberg, University of Toronto

Experimental measurement tradeoffs, from Heisenberg to Aharonov to quantum data compression

Tradeoffs in measurement and information are among the central themes of quantum mechanics.  I will try to summarize in this talk a few of our experiments related to modern views of these topics.  In particular, I will try to give an example or two of the power of "weak measurements," both for fundamental physics and for possible precision metrology.  One example will involve revisiting the question of Heisenberg's famous principle, and an interpretation which is widespread but has now been experimentally shown to be incorrect.   Then I will also discuss our recent work on a "quantum data compression" protocol which would allow a small-scale quantum memory to store all the extractable information from a larger ensemble of identically prepared systems. Finally, I will talk about our experiment entangling two optical beams to demonstrate "weak-value amplification," and the ongoing controversy about when if ever this technique could be useful in practice.

 

 

 

Friday Sep 23, 2016

Understanding the causal influences that hold among the parts of a system is critical both to explaining that system's natural behaviour and to controlling it through targeted interventions. In a quantum world, understanding causal relations is equally important, but the set of possibilities is far richer. The two basic ways in which a pair of time-ordered quantum systems may be causally related are by a cause-effect mechanism or by a common cause acting on both. Here, we show that it is possible to have a coherent mixture of these two possibilities.

Scientific Areas: 

 

Friday Sep 23, 2016
Speaker(s): 

Sets or pairs of incompatible observables, such as momentum and position, play a pivotal role in a wide range of distinctly quantum effects and applications, including quantum cryptography, the Heisenberg Uncertainty Principle, quantum state tomography, and Bell’s inequalities. In particular, in quantum physics, we are prohibited from precisely measuring the values of incompatible observables, a fact that is at the heart of the nature of the quantum state. In this talk, I will explore an assortment of strategies that simple-mindedly attempt to circumvent this prohibition.

Scientific Areas: 

 

Friday Sep 23, 2016
Speaker(s): 

Tradeoffs in measurement and information are among the central themes of quantum mechanics. I will try to summarize in this talk a few of our experiments related to modern views of these topics. In particular, I will try to give an example or two of the power of "weak measurements," both for fundamental physics and for possible precision metrology. One example will involve revisiting the question of Heisenberg's famous principle, and an interpretation which is widespread but has now been experimentally shown to be incorrect.

Scientific Areas: 

 

Friday Sep 23, 2016
Speaker(s): 

One of the most successful theories in physics until now is quantum mechanics. However, the physical origins of its mathematical structure are still under debate, and a "generalized" quantum theory to unify quantum mechanics and gravity is still missing. Recently, in an effort to better understand the mathematical structure of quantum mechanics, theories containing the essence of quantum mechanics, while also having a broader description of physical phenomena, have been proposed. These so-called "post-quantum theories" have only been recently tested at the lab.

Scientific Areas: 

 

Friday Sep 23, 2016

The scientific journey from the first hints of quantum behaviour to the Bloch sphere in your textbook was a long and tortuous one. But using some of the technological and conceptual fruits of that journey, we show that an experiment can manifest the Bloch sphere via an analysis that doesn't require any quantum theory at all. Our technique is to fit experimental data to a generalised probabilistic theory, which allows us to infer both the dimension and shape of the state and measurement spaces of the system under study.

Scientific Areas: 

Scientific Organizers:

  • Kevin Resch, University of Waterloo
  • Robert Spekkens, Perimeter Institute