9 papers
Characterizing unitaries via quasi-process functions
Nasra Daher Ahmed, Ravi Kunjwal
It is well-known that every n-qubit unitary can be decomposed into a product of controlled single-qubit unitaries. We show that the control conditions in such a decomposition natur…
Causal inequalities witness non-stabilizerness
Leonardo Vaglini, Nasra Daher Ahmed, Ravi Kunjwal
Stabilizer operations describe a fragment of quantum theory that is known to be efficiently classically simulable, thanks to the Gottesman-Knill theorem. For this reason, nonstabil…
What makes a causal loop consistent?
Hippolyte Dourdent, Andreas Leitherer, Emanuel-Cristian Boghiu +3
Causal loops escape paradoxes if they generate valid probabilities under arbitrary independent local interventions. We show that a deterministic classical process is logically cons…
Indefinite Causal Order Reverses the Real-Complex Hierarchy
Jacopo Surace, Shintaro Minagawa, Ravi Kunjwal
[Note added after submission. After posting the first version of this preprint and corresponding with Ved Kunte and Kuntal Sengupta, we identified an issue with the claimed separat…
All star-incompatible measurements can certify steering-based randomness
Shintaro Minagawa, Ravi Kunjwal
Certifying that quantum randomness generated by untrusted devices is unpredictable to an attacker (say, Eve) is crucial for device-independent security. Bipartite protocols where o…
Quantumness via Discrete Structures
Ravi Kunjwal
Quantum theory departs from classical probabilistic theories in foundational ways. These departures--termed quantumness here--power quantum information and computation. This thesis…
Paradox-free classical non-causality and unambiguous non-locality without entanglement are equivalent
Hippolyte Dourdent, Kyrylo Simonov, Andreas Leitherer +5
Closed timelike curves (CTCs) challenge our conception of causality by allowing information to loop back into its own past. Any consistent description of such scenarios must avoid…
No-go theorem for quantum realization of extremal correlations
Sujan V. K, Ravi Kunjwal
The study of quantum correlations is central to quantum information and foundations. The paradigmatic case of Bell scenarios considers product measurements implemented on a multipa…
Generalizing Bell nonlocality without global causal assumptions
Ravi Kunjwal, Ognyan Oreshkov
Bell scenarios are multipartite scenarios that exclude any communication between parties. This constraint leads to a strict hierarchy of correlation sets in such scenarios, namely,…