Abstract In this talk, we will deal with the mathematics of non Abelian anyon physics of Majorana Fermion.

Abstract We consider multi-party quantum sequence discrimination under local operations and classical communication(LOCC), and provide conditions under which the optimal LOCC discrimination of a multi-party quantum sequence ensemble can be factorized into that of each individual ensemble. In other words, the optimal LOCC discrimination of a multi-party quantum sequence ensemble can be achieved just by performing optimal LOCC discrimination independently at each step of the quantum sequence. We also illustrate through examples of multi-party quantum states that such factorizability of optimal LOCC discrimination is possible. We further establish a necessary and sufficient condition under which the optimal LOCC discrimination of a multi-party quantum state ensemble can be realized just by guessing the state with the largest probability. Our results can provide a useful application to investigate the fundamental limits of quantum data hiding.

Abstract Optimal quantum measurements are typically assumed to destroy the initial state of a system, leaving any encoded information inaccessible to subsequent observers. The use of weak measurements, however, allows us to go beyond this picture. In this talk, I will introduce our recent work on sequential quantum state discrimination, in which multiple observers aim to determine the initial state of a single system. We study in particular the use of maximum confidence measurements. For certain ensembles it will be seen that, remarkably, any number of parties may obtain equally high confidence. Our results open up new possibilities for the sharing of quantum resources among multiple parties.

Abstract A noisy intermediate-scale quantum(NISQ) semidefinite programming(SDP) solver has recently been proposed, providing a convex variational framework in which the classical subproblem is itself an SDP defined over a low-dimensional ansatz space. While its applicability to unambiguous quantum state discrimination was demonstrated, the study was limited to a narrow setting without systematic analysis. In this work, we investigate the performance of the NISQ SDP solver in more general settings through several representative examples, analyzing the effects of ansatz design, sampling errors, and hardware noise. We identify conditions under which the solver can be effectively employed and demonstrate its potential as a practical near-term approach to semidefinite optimization in quantum information.

Venue Centum Mama Buffet

Abstract We consider entanglement distillation with noisy operations in which quantum measurements that constitute a general quantum operation are particularly noisy. We present a protocol for purifying noisy measurements and show that imperfect local operations can distill entanglement. The protocol works for arbitrary noisy measurements in general and is cost-effective and resource-efficient with a single additional qubit per party to resolve the distillation of entanglement. Additionally, we propose an entanglement purification protocol by quantum communication that does not consume entangled pairs. The purification protocol is feasible with currently available quantum technologies and readily applied to entanglement applications.

Abstract In this talk, I will briefly introduce how quantum machine learning can be applied to research on quantum state discrimination and quantum channel discrimination. To do this, I will introduce prior research on quantum machine learning conducted by Team QST, and discuss future research plans for quantum discriminations. If time permits, I will also introduce Team QST's various research and activities.

Abstract Useful applications of quantum information technologies can be found by identifying tasks in which quantum resources outperform their classical counterparts. In this work, we introduce a two-party communication primitive, random exclusion code (REC), which is a single-shot prepare-and-measure protocol where a sender encodes a random message into a shorter sequence and a receiver attempts to exclude a randomly chosen letter in the original message. We present quantum advantages in RECs in two ways: probability and dimension. We show that RECs with quantum resources achieve higher success probabilities than classical strategies. We verify that, with the additional constraint that successful outcomes occur uniformly and without error, the quantum resources required to describe detection events of RECs have a smaller dimension than classical ones. We also show that a guessing counterpart, random access codes (RACs), may not have a dimension advantage over classical resources. Our results elucidate various possibilities of achieving quantum advantages in two-party communication.

Abstract A measurement setting for quantum state identification, namely tomographically complete measurements, can verify all properties of quantum states; once a state is verified, one can determine its properties, such as entanglement, purity, fidelity, correlation functions, etc. A fraction of the measurement results, yet insufficient to verify a state, may reveal specific properties of a state. In this work, we establish a practical, efficient framework for verifying entangled states when a measurement setting is provided. We construct observables, called entanglement witnesses (EWs), that can distinguish entangled states from separable ones from tomographically incomplete measurements. We show that estimating a few Pauli observables can construct many EWs. We also present a proof-of-principle demonstration of detecting entangled states with photon-polarization qubits. Our results find the maximal usefulness of an incomplete measurement setting for detecting entangled states.

Abstract Unlike classical correlations, entanglement cannot be freely shared among multiple parties. This unique feature of quantum systems is known as the monogamy of entanglement. While it holds for all multipartite pure states, its converse — weak entanglement between two parties enforces strong entanglement with a third party — occurs only under specific conditions. In particular, Hayashi and Chen [Phys. Rev. A 84, 012325 (2011)] demonstrated a qualitative version of the converse monogamy of entanglement (CMoE) for tripartite pure states by employing a hierarchy of bipartite entanglement defined through the relations among various separability criteria, and Singh and Datta [IEEE Trans. Inf. Theory 69, 6564 (2023)] later extended this notion of the CMoE from the viewpoint of distillability under one-way or two-way classical communication. In this work, we extend their results to the CMoE with broader conditions, and furthermore show that our extensions are maximal with respect to the hierarchies they considered.