09:00 to 10:30 
Serge Rosenblum (Weizmann Institute, Israel) 
Quantum Error Correction (Lecture 3) We'll explore quantum error correction fundamentals, starting with decoherence and key principles of QEC codes. Our discussion will extend to stabilizer and topological codes, as well as more advanced coding schemes. Time permitting, we'll also review the current state of quantum computing across different technologies.



11:00 to 11:30 
Gerardo Ortiz (Indiana University, USA) 
Entangled Probes for Entangled Matter Advancing the frontiers of science often requires the creation of new probes to uncover the underlying microscopic mechanisms giving rise to exotic macroscopic phenomena, such as hightemperature superconductivity. Can quantum entangled probes uncover the inherent entanglement of the target matter? We have recently developed an entangled neutron beam where individual neutrons can be entangled in spin, trajectory, and energy. To demonstrate entanglement in these beams we crafted neutron interferometric measurements of contextuality inequalities whose violation provided an indication of the breakdown of Einstein's local realism. In turn, the tunable entanglement (spinecho) length of the neutron beam from nanometers to microns and energy differences from peV to neV opens a pathway to a future era of entangled neutron scattering in matter. What kind of information can be extracted with this novel entangled probe? A recent general quantum manybody entangledprobe scattering theory provides a framework to respond to this question. Interestingly, by carefully tuning the probe's entanglement and inherent coherence properties, one can directly access the intrinsic entanglement of the target material. This theoretical framework supports the view that our entangled beam can be used as a multipurpose scientific tool. We are currently pursuing several new ideas and developing spintextured entangled beams with orbital angular momentum for future experiments in candidate quantum spin liquids, unconventional superconductors, and chiral quantum materials.



11:40 to 12:10 
Urbasi Sinha (RRI, India) 
Revealing new facets in experimental quantum information processing with photons We present new facets in the domain of photonic quantum information processing (QIP). A major part of the talk focuses on our recent works in higher dimensional QIP.
We provide a novel scheme for direct determination of different entanglement monotones used to quantify entanglement in arbitrary system dimensions using only one pair of complementary observables, as opposed to the standard d^2 measurements needed in d dimensions. In our scheme, we analytically relate statistical measures of correlations i.e. Pearson Correlation Coefficient, Mutual Predictability and Mutual Information with the standard measures of entanglement i.e. Negativity and Entanglement of Formation for arbitrary dimensional states. In [1], we theoretically formulate, experimentally implement and explore implications of the scheme for actually determining values of the entanglement measures for the first time making use of the standard statistical correlators, essentially for twoqudit pure states. The extension to mixed states is thoroughly studied in [2], showing that the efficacy of this scheme is restricted to not only distillable entangled states, but extends to bound entangled states as well.
Next we discuss our novel approach to higher dimensional quantum state estimation, using interference as a tool [3]. Here we present an interferometric method, in which any qubit state, whether mixed or pure, can be inferred from the visibility, phase shift, and average intensity of an interference pattern using a singleshot measurement—hence, we call it Quantum State Interferography [3]. This provides us with a “black box” approach to quantum state estimation, wherein, between the incidence and extraction of state information, we are not changing any conditions within the setup, thus giving us a true single shot estimation of the quantum state. An extension of the scheme to pure states involving d−1 interferograms for ddimensional systems (qudits) is also presented. The scaling gain is even more dramatic in the qudit scenario for our method, where, in contrast, standard QST, scales roughly as d2.
In the final part, we briefly present the first loopholefree experiment wherein both the LGI and the WLGI inequalities have been decisively violated using single photons[4], thus providing a comprehensive refutation of the classical realist worldview along with measurements ensured to be noninvasive. This provides a powerful platform for harnessing this most general unambiguous signature of nonclassicality of single photon states towards various information theoretic applications wherein the single photon is a ubiquitous workhorse.
[1] Direct determination of entanglement monotones for arbitrary dimensional bipartite states using statistical correlators and one set of complementary measurements, D. Ghosh, T.Jennewein, U.Sinha, Quantum Science and Technology, 7 045037, 2022.
[2] Relating an entanglement measure with statistical correlators for twoqudit mixed states using only a pair of complementary observables, S. Sadana, S. Kanjilal, D.Home, U.Sinha, arXiv: 2201.06188, 2022.
[3] Quantum State Interferography, S.Sahoo, S. Chakraborti, A.K.Pati, U.Sinha, Phys. Rev. Lett. 125 123601, 2020.
[4] Loophole free interferometric test of macrorealism using heralded single photons, K.Joarder, D.Saha, D.Home, U.Sinha, PRX Quantum, 3, 010307, 2022.



12:20 to 12:50 
Arijit Saha (IOPB, India) 
Topological Superconductivity by Engineering Noncollinear Magnetism in Magnet/Superconductor Heterostructures Our theoretical investigation explores a feasible route to engineer the twodimensional (2D) Kitaev model of firstorder topological superconductivity (TSC) introducing a magnetic spin texture. The main outcome of 2D Kitaev’s model is that a px + py type superconductor can exhibit a gapless topological superconducting phase in bulk hosting nondispersive Majorana flat edge mode (MFEM) at the boundary. Our proposed general minimal model Hamiltonian is suitable to describe magnet/superconductor heterostructure. It reveals robust MFEM within the emergent gap of Shiba bands, spatially localised at the edges of a 2D magnetic domain of spinspiral. We finally verify this concept from real material perspectives by considering Mn (Cr) monolayer grown on an swave superconducting substrate, Nb(110) under strain (Nb(001)). In both the 2D cases, the antiferromagnetic spinspiral solutions exhibit robust MFEM at certain domain edges. This approach, particularly when the MFEM appears in the TSC phase for such heterostructure materials, offers significant prospect to extend the realm of TSC in 2D. Very recently, we expand this theoretical framework for engineering a 2D secondorder topological superconductor (SOTSC) by utilising a heterostructure: incorporating noncollinear magnetic textures between an swave superconductor and a 2D quantum spin Hall insulator. It stabilises the higher order topological superconducting phase, resulting in Majorana corner modes (MCMs) at the four corners of a 2D domain. Such first and second order Majorana modes are believed to be the building blocks for the faulttolerant topological quantum computation.



15:00 to 15:30 
Alexander Altland (ITP, TU Wien, Austria) 
Quantum computers challenged by manybody chaos From the perspective of manybody physics, the transmon qubit architectures currently developed for quantum computing are systems of coupled nonlinear quantum resonators. A significant amount of intentional frequency detuning (disorder) is required to protect individual qubit states against the destabilizing effects of nonlinear resonator coupling. In this talk, we will discuss the stability of this variant of a manybody localized phase for system parameters relevant to current quantum processors. An essential element in of our diagnostic toolbox are classical simulations, which can be run, e.g., for upcoming IBM designs comprising hundreds of qubits. The overall conclusion of this study is that it will take considerable engineering efforts to protect transmon quantum computers from the destructive influence of chaotic fluctuations.



15:40 to 16:10 
Igor Gornyi (KIT, Germany) 
Free fermions under random measurements An analytical approach to studying free fermions subject to random measurements of local site occupation numbers is developed, based on the Keldysh sigma model and replica trick. On the Gaussian level, this theory predicts a logarithmic behavior for the entanglement entropy of onedimensional systems. However, the oneloop renormalization group analysis demonstrates that this logarithmic growth saturates at a finite value even for rare measurements, through "weaklocalization" quantum corrections similar to those in 2D disordered systems. This yields the arealaw phase in the thermodynamic limit and implies the absence of a measurementinduced entanglement phase transition for monitored 1D free fermions. For 2D free fermions, this approach predicts the entanglement transition from the arealaw to the critical phase. No volumelaw phase is realized for fermions in arbitrary dimensions in the absence of interactions.



16:20 to 16:50 
Udit Khanna (BarIlan University, Israel) 
Quantum Hall Phase Diagram of Bilayer Graphene Bilayer graphene exhibits a rich phase diagram in the quantum Hall (QH) regime, arising from a multitude of internal degrees of freedom, including spin, valley, and orbital indices. The variety of fractional QH states between filling factors 1 and 2 suggests, among other things, a quantum phase transition between valleypolarized and unpolarized states at a perpendicular electricfield D*. We find that the behavior of D* with filling factor changes markedly as the magnetic field B is reduced. We present a theoretical model for latticescale interactions, which explains these observations; contrary to earlier studies, it involves finiteranged terms comprising both repulsive and attractive components. Within this model, we analyze the nature of the phase at filling factor 2, and predict that valleycoherence may emerge at high B fields. This suggests that the system may support bondordered phases which may be amenable to experimental verification.


