Journal Article: Bell’s theorem for temporal order
Zych, Magdalena, Costa, Fabio, Pikovski, Igor and Brukner, Časlav (2019) Bell’s theorem for temporal order. Nature Communications, 10 1: . doi:10.1038/s41467-019-11579-x
Journal Article: Quantum Markovianity as a supervised learning task
Shrapnel, Sally, Costa, Fabio and Milburn, Gerard (2018) Quantum Markovianity as a supervised learning task. International Journal of Quantum Information, 16 08: 1840010. doi:10.1142/s0219749918400105
Journal Article: Indefinite causal order in a quantum switch
Goswami, K., Giarmatzi, C., Kewming, M., Costa, F., Branciard, C., Romero, J. and White, A. G. (2018) Indefinite causal order in a quantum switch. Physical Review Letters, 121 9: 090503. doi:10.1103/physrevlett.121.090503
Principles and applications of quantum causal discovery
(2017–2020) ARC Discovery Early Career Researcher Award
Quantum Causal Structures (Templeton Grant administered by Austrian Academy of Sciences)
(2016–2019) Austrian Academy of Sciences
General Relativistic Effects in Quantum Systems
Doctor Philosophy
Quantum Mechanics Near Closed Timelike Curves
Doctor Philosophy
Informational approaches to causal asymmetry
Doctor Philosophy
All fundamental interactions known in nature are local: only close-by systems can interact. But where does the very notion of closeness come from? Ultimately, we only learn about spatial relations through physical systems, it should thus be possible to understand the locality of interactions without pre-assuming the existence of an absolute space.
The aim of the project is to derive the local structure of quantum systems from properties of dynamics alone, with no reference to any underlying geometry. Formally, the task is to derive a decomposition of Hilbert space in tensor factors, with each factor representing a local subsystem, from basis-independent properties of the Hamiltonian.
Available as Honours Project.
Quantum Information on indefinite causal structure
Quantum information has developed in the last decades into a broad field, offering several promising applications for future technology and deep insights into the foundations of physics. Very recently, first steps have been made in the direction of theoretically characterising and experimentally manipulating causal relations between quantum systems from an information-theoretical perspective. The motivations are two-fold: from a foundational perspective, it is expected that the notion of definite, classical causal structure would not survive in a theory where gravity, and thus space-time, are subject to quantum effects. More practically, it has been proposed that quantum causal relations can also be realised in laboratory experiments and that they can provide advantage for several tasks, such as computation and communication complexity.
As this is a very new field, it still needs development of basic tools and exemplary protocols. To name but a few possibilities:
· Communication: how does indefinite causal structure affect the possibility of communicating classical or quantum information?
· Discrimination of causal structure: Given a set of events and some prior information about their causal relations, what are the optimal protocols for inferring the causal structure?
· Teleportation of causal structure: is it possible to exploit “entangled causal relations” to effectively teleport an unknown causal structure from a set of events to another?
· Information measures on indefinite causal structure: what are meaningful ways to quantify information encoded in systems with indefinite causal structure? Is it possible to quantify information about the causal structure itself?
The aim of the project is to develop some of these tools, having in mind potential applications to information-theoretical tasks, quantum technologies, or foundational questions.
Available both as Honours or PhD Project.
Bell’s theorem for temporal order
Zych, Magdalena, Costa, Fabio, Pikovski, Igor and Brukner, Časlav (2019) Bell’s theorem for temporal order. Nature Communications, 10 1: . doi:10.1038/s41467-019-11579-x
Quantum Markovianity as a supervised learning task
Shrapnel, Sally, Costa, Fabio and Milburn, Gerard (2018) Quantum Markovianity as a supervised learning task. International Journal of Quantum Information, 16 08: 1840010. doi:10.1142/s0219749918400105
Indefinite causal order in a quantum switch
Goswami, K., Giarmatzi, C., Kewming, M., Costa, F., Branciard, C., Romero, J. and White, A. G. (2018) Indefinite causal order in a quantum switch. Physical Review Letters, 121 9: 090503. doi:10.1103/physrevlett.121.090503
Multi-time quantum correlations with no spatial analog
Ringbauer, Martin, Costa, Fabio, Goggin, Michael E., White, Andrew G. and Fedrizzi, Alessandro (2018) Multi-time quantum correlations with no spatial analog. npj Quantum Information, 4 1: . doi:10.1038/s41534-018-0086-y
Unifying framework for spatial and temporal quantum correlations
Costa, Fabio, Ringbauer, Martin, Goggin, Michael E., White, Andrew G. and Fedrizzi, Alessandro (2018) Unifying framework for spatial and temporal quantum correlations. Physical Review A, 98 1: . doi:10.1103/PhysRevA.98.012328
Causation does not explain contextuality
Shrapnel, Sally and Costa, Fabio (2018) Causation does not explain contextuality. Quantum, 2 63. doi:10.22331/q-2018-05-18-63
Shrapnel, Sally, Costa, Fabio and Milburn, Gerard (2018) Updating the Born rule. New Journal of Physics, 20 5: 053010. doi:10.1088/1367-2630/aabe12
A quantum causal discovery algorithm
Giarmatzi, Christina and Costa, Fabio (2018) A quantum causal discovery algorithm. Npj Quantum Information, 4 1: . doi:10.1038/s41534-018-0062-6
Genuinely multipartite noncausality
Abbott, Alastair A., Wechs, Julian, Costa, Fabio and Branciard, Cyril (2017) Genuinely multipartite noncausality. Quantum, 1 39. doi:10.22331/q-2017-12-14-39
Time dilation in quantum systems and decoherence
Pikovski, Igor, Zych, Magdalena, Costa, Fabio and Brukner, Časlav (2017) Time dilation in quantum systems and decoherence. New Journal of Physics, 19 2: 025011. doi:10.1088/1367-2630/aa5d92
Multipartite causal correlations: polytopes and inequalities
Abbott, Alastair A., Giarmatzi, Christina, Costa, Fabio and Branciard, Cyril (2016) Multipartite causal correlations: polytopes and inequalities. Physical Review A, 94 3: 032131-1-032131-12. doi:10.1103/PhysRevA.94.032131
Experimental test of nonlocal causality
Ringbauer, Martin, Giarmatzi, Christina, Chaves, Rafael, Costa, Fabio, White, Andrew G. and Fedrizzi, Alessandro (2016) Experimental test of nonlocal causality. Science Advances, 2 8: . doi:10.1126/sciadv.1600162
Costa, Fabio and Shrapnel, Sally (2016) Quantum causal modelling. New Journal of Physics, 18 6: . doi:10.1088/1367-2630/18/6/063032
Reply to 'Questioning universal decoherence due to gravitational time dilation'
Pikovski, Igor, Zych, Magdalena, Costa, Fabio and Brukner, Caslav (2016) Reply to 'Questioning universal decoherence due to gravitational time dilation'. Nature Physics, 12 1: 2-3. doi:10.1038/nphys3650
The simplest causal inequalities and their violation
Branciard, Cyril Branciard, Araujo, Mateus, Feix, Adrien, Costa, Fabio and Brukner, Caslav (2015) The simplest causal inequalities and their violation. New Journal of Physics, 18 1: . doi:10.1088/1367-2630/18/1/013008
Witnessing causal nonseparability
Araujo, Mateus, Branciard, Cyril, Costa, Fabio, Feix, Adrien, Giarmatzi, Christina and Brukner, Caslav (2015) Witnessing causal nonseparability. New Journal of Physics, 17 10: . doi:10.1088/1367-2630/17/10/102001
Experimental superposition of orders of quantum gates
Procopio, Lorenzo M., Moqanaki, Amir, Araujo, Mateus, Costa, Fabio, Calafell, Irati A., Dowd, Emma G., Hamel, Dendy R., Rozema, Lee A., Brukner, Caslav and Walther, Philip (2015) Experimental superposition of orders of quantum gates. Nature Communications, 6 7913: 1-6. doi:10.1038/ncomms8913
Universal decoherence due to gravitational time dilation
Pikovski, Igor, Zych, Magdalena, Costa, Fabio and Brukner, Caslav (2015) Universal decoherence due to gravitational time dilation. Nature Physics, 11 8: 668-672. doi:10.1038/nphys3366
Computational advantage from quantum-controlled ordering of gates
Araujo, Mateus, Costa, Fabio and Brukner, Caslav (2014) Computational advantage from quantum-controlled ordering of gates. Physical Review Letters, 113 25: 250402-1-250402-5. doi:10.1103/PhysRevLett.113.250402
Renormalized entropy of entanglement in relativistic field theory
Ibnouhsein, Issam, Costa, Fabio and Grinbaum, Alexei (2014) Renormalized entropy of entanglement in relativistic field theory. Physical Review D, 90 6: . doi:10.1103/PhysRevD.90.065032
Quantum circuits cannot control unknown operations
Araujo, Mateus, Feix, Adrien, Costa, Fabio and Brukner, Caslav (2014) Quantum circuits cannot control unknown operations. New Journal of Physics, 16 . doi:10.1088/1367-2630/16/9/093026
General relativistic effects in quantum interference of photons
Zych, Magdalena, Costa, Fabio, Pikovski, Igor, Ralph, Timothy C. and Brukner, Caslav (2012) General relativistic effects in quantum interference of photons. Classical and Quantum Gravity, 29 22: 224010-1-224010-18. doi:10.1088/0264-9381/29/22/224010
Quantum correlations with no causal order
Oreshkov, Ognyan, Costa, Fabio and Brukner, Caslav (2012) Quantum correlations with no causal order. Nature Communications, 3 1: . doi:10.1038/ncomms2076
Quantum interferometric visibility as a witness of general relativistic proper time
Zych, Magdalena, Costa, Fabio, Pikovski, Igor and Brukner, Caslav (2011) Quantum interferometric visibility as a witness of general relativistic proper time. Nature Communications, 2 1: . doi:10.1038/ncomms1498
Entanglement between smeared field operators in the Klein-Gordon vacuum
Zych, Magdalena, Costa, Fabio, Kofler, Johannes and Brukner, Caslav (2010) Entanglement between smeared field operators in the Klein-Gordon vacuum. Physical Review D: covering particles, fields, gravitation, and cosmology, 81 12: . doi:10.1103/PhysRevD.81.125019
Entanglement detection with bounded reference frames
Costa, Fabio, Harrigan, Nicholas, Rudolph, Terry and Brukner, Caslav (2009) Entanglement detection with bounded reference frames. New Journal of Physics, 11 . doi:10.1088/1367-2630/11/12/123007
Modeling a particle detector in field theory
Costa, Fabio and Piazza, Federico (2009) Modeling a particle detector in field theory. New Journal of Physics, 11 . doi:10.1088/1367-2630/11/11/113006
Renormalized thermal entropy in field theory
Cacciatori, Sergio L., Costa, Fabio and Piazza, Federico (2009) Renormalized thermal entropy in field theory. Physical Review D, 79 2: . doi:10.1103/PhysRevD.79.025006
Spatial modes for testing indefinite causal order
Romero, Jacquiline, Goswami, Kaumudibikash, Giarmatzi, Christina, Costa, Fabio, Branciard, Cyril and White, Andrew G. (2018). Spatial modes for testing indefinite causal order. In: David L. Andrews, Enrique J. Galvez and Jesper Glückstad, Complex Light and Optical Forces XII. Complex Light and Optical Forces XII 2018, San Francisco, CA, United States, (). 30 January - 1 February 2018. doi:10.1117/12.2292732
Experimental test of nonlocal causality
Ringbauer, M., Giarmatzi, C., Chaves, R., Costa, F., White, A. G. and Fedrizzi, A. (2017). Experimental test of nonlocal causality. In: 2017 Conference On Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Munich, Germany, (). 25-29 June 2017. doi:10.1109/CLEOE-EQEC.2017.8087316
General relativistic effects in quantum interference of "clocks"
Zych, M., Pikovski, I., Costa, F. and Brukner, C. (2016). General relativistic effects in quantum interference of "clocks". In: 8th Symposium on Frequency Standards and Metrology 2015. 8th Symposium on Frequency Standards and Metrology 2015, Potsdam, Germany, (). 12 - 16 October 2015. doi:10.1088/1742-6596/723/1/012044
Experimental superposition of orders of quantum gates
Procopio, L. M., Moqanaki, A., Araújo, M., Costa, F., Calafell, I. A., Dowd, E. G., Hamel, D. R., Rozema, L. A., Brukner, C. and Walther, P. (2014). Experimental superposition of orders of quantum gates. In: European Quantum Electronics Conference , Munich, Germany, (). 21–25 June 2015.
Volumes of space as subsystems
Piazza, Federico and Costa, Fabio (2007). Volumes of space as subsystems. In: , , (). .
Principles and applications of quantum causal discovery
(2017–2020) ARC Discovery Early Career Researcher Award
Quantum Causal Structures (Templeton Grant administered by Austrian Academy of Sciences)
(2016–2019) Austrian Academy of Sciences
General Relativistic Effects in Quantum Systems
Doctor Philosophy — Principal Advisor
Other advisors:
Quantum Mechanics Near Closed Timelike Curves
Doctor Philosophy — Associate Advisor
Other advisors:
Informational approaches to causal asymmetry
Doctor Philosophy — Associate Advisor
Other advisors:
Rethinking causality in quantum mechanics
(2018) Doctor Philosophy — Associate Advisor
Other advisors:
Note for students: The possible research projects listed on this page may not be comprehensive or up to date. Always feel free to contact the staff for more information, and also with your own research ideas.
All fundamental interactions known in nature are local: only close-by systems can interact. But where does the very notion of closeness come from? Ultimately, we only learn about spatial relations through physical systems, it should thus be possible to understand the locality of interactions without pre-assuming the existence of an absolute space.
The aim of the project is to derive the local structure of quantum systems from properties of dynamics alone, with no reference to any underlying geometry. Formally, the task is to derive a decomposition of Hilbert space in tensor factors, with each factor representing a local subsystem, from basis-independent properties of the Hamiltonian.
Available as Honours Project.
Quantum Information on indefinite causal structure
Quantum information has developed in the last decades into a broad field, offering several promising applications for future technology and deep insights into the foundations of physics. Very recently, first steps have been made in the direction of theoretically characterising and experimentally manipulating causal relations between quantum systems from an information-theoretical perspective. The motivations are two-fold: from a foundational perspective, it is expected that the notion of definite, classical causal structure would not survive in a theory where gravity, and thus space-time, are subject to quantum effects. More practically, it has been proposed that quantum causal relations can also be realised in laboratory experiments and that they can provide advantage for several tasks, such as computation and communication complexity.
As this is a very new field, it still needs development of basic tools and exemplary protocols. To name but a few possibilities:
· Communication: how does indefinite causal structure affect the possibility of communicating classical or quantum information?
· Discrimination of causal structure: Given a set of events and some prior information about their causal relations, what are the optimal protocols for inferring the causal structure?
· Teleportation of causal structure: is it possible to exploit “entangled causal relations” to effectively teleport an unknown causal structure from a set of events to another?
· Information measures on indefinite causal structure: what are meaningful ways to quantify information encoded in systems with indefinite causal structure? Is it possible to quantify information about the causal structure itself?
The aim of the project is to develop some of these tools, having in mind potential applications to information-theoretical tasks, quantum technologies, or foundational questions.
Available both as Honours or PhD Project.