Quantum Information in Spain ICE-8

Session

Session 4.2

29 May 2023, 11:20

Santiago de Compostela

Conveners

Session 4.2

• Chair: Marcos Curty (Universidad de Vigo)

Session 4.2

• Chair: David Zueco (Instituto de Nanociencia y Materiales de Aragon)

Session 4.2

• Chair: Andres Gomez Tato

Session 4.2

• Chair: Alba Cervera Lierta (Barcelona Supercomputing Center)

120. KeySight

Benjamín García (KEYSIGHT TECHNOLOGIES SPAIN), Miguel Ángel Fernández (KEYSIGHT TECHNOLOGIES SPAIN)

29/05/2023, 11:20

61. Fast single-photon detectors and real-time key distillation enable high secret-key-rate quantum key distribution systems

Dr Fadri Gruenenfelder (University of Vigo)

29/05/2023, 11:40

Talk

We implemented a simplified time-bin BB84 quantum key distribution protocol with the purpose of achieving the highest possible secret key rate at short distances. The sender Alice emits signals at a rate of 2.5 GHz. In the key-generating basis, we use a superconducting nanowire single photon detector (SNSPD) with a novel design optimized for fast count rates. The in-house designed and...

58. Distributing circuits over heterogeneous, modular quantum computing network architectures

Pablo Andres-Martinez (Quantinuum)

29/05/2023, 12:00

Talk

We consider a heterogeneous network of quantum computing modules, sparsely connected via Bell states. Operations across these connections constitute a computational bottleneck and they are likely to add more noise to the computation than operations performed within a module. We introduce several techniques for transforming a given quantum circuit into one implementable on a network of the...

54. Topologically robust network nonlocality

Tamás Kriváchy (TU Wien)

29/05/2023, 12:20

Talk

In recent years, the study of Bell-type nonlocality on networks has led to an array of intriguing foundational results. Nonetheless the field still faces difficulties in finding a justified application. One of the key barriers for this is the assumption of independent sources in network nonlocality, which is difficult to enforce. In our work we examine a possible operational interpretation for...

41. Guaranteeing non-classicality in experimental quantum networks without assuming quantum mechanics

Alejandro Pozas-Kerstjens (Institute of Mathematical Sciences (ICMAT-CSIC))

29/05/2023, 12:40

Talk

Quantum technologies promise interesting new approaches to areas such as computing and communication. A branch that is becoming increasingly interesting is that of quantum networks. The technological assets for quantum networks have been developing rapidly in recent years and many implementations, often geared towards quantum cryptography, have been reported. In order to demonstrate security...

122. Quantum Computing at FUJITSU

Juan Antonio García Carrasco

30/05/2023, 11:20

27. Using high-dimensional entanglement for closing the detection loophole in Bell experiments

Adán Cabello

30/05/2023, 11:40

Talk

I present two approaches for closing the detection loophole in Bell experiments. Both exploit that high-dimensional entanglement allows for loophole-free experiments with low detection efficiency.

The "penalized N-product Bell inequalities" [1] is a method for, starting from any qudit-qudit correlation violating a Bell inequality with a certain critical detection efficiency, identifying...

80. Number-phase uncertainty relations and bipartite entanglement detection in spin ensembles

Geza Toth (University of the Basque Country UPV/EHU)

30/05/2023, 12:00

Talk

We present a method to detect bipartite entanglement based on number-phase-like uncertainty relations in split spin ensembles. First, we derive an uncertainty relation that plays the role of a number-phase uncertainty for spin systems. It is important that the relation is given with well-defined and easily measurable quantities, and that it does not need assuming infinite dimensional systems....

67. Quantum supremacy in mechanical tasks: projectiles, rockets and quantum backflow

Mr David Trillo (IQOQI Vienna)

30/05/2023, 12:20

Talk

While current research in quantum theory focuses on the exploitation of quantum effects in communication and computation scenarios, quantum systems are also known to be advantageous for some mechanical tasks. The most known effect is that of tunneling, but there are other less well known effects. One of those is quantum backflow [1], a phenomenon in which a free quantum particle with positive...

19. Optimal control of dissipation and work fluctuations for rapidly driven systems

Alberto Rolandi

30/05/2023, 12:40

Talk

To achieve efficient and reliable control of microscopic systems one should look for driving protocols that mitigate both the average dissipation and stochastic fluctuations in work. This is especially important in fast driving regimes in which the system is driven far out of equilibrium, potentially creating large amounts of unwanted entropy production. Here we characterise these optimal...

127. EVIDEN-ATOS

José Camacho

31/05/2023, 11:20

89. Variational Waveguide-QED Simulators

Cristian Tabares López (Institute of Fundamental Physics (IFF-CSIC))

31/05/2023, 11:40

Talk

Variational Quantum Algorithms (VQAs) [1] use a classical optimizer to train a parametrized quantum circuit (PQC). These have emerged as a practical way to exploit state-of-the-art quantum computers. Currently, most VQAs have been designed for fully digital approaches, in which the error ends up accumulating for circuits with many parameters. A possible way out is the use of analogue...

4. Tackling thermalization dynamics through decoherent tensor networks

Carlos Ramos Marimón (Universitat de Barcelona)

01/06/2023, 11:20

Talk

Classical simulation of quantum dynamics from many-body systems with tensor networks is hindered by the exponential growth of entanglement contained at the bonds of a chosen wavefunction factorization (typically Matrix Product States). Modern algorithms try to overcome this entanglement barrier by folding and contracting transversely the network [1], or optimizing schemes to exploit only...

40. Exact solution for quantum strong long-range models using a generalized Hubbard–Stratonovich transformation from cavity QED

Juan Román-Roche (Instituto de Nanociencia y Materiales de Aragón)

01/06/2023, 11:40

Talk

The field of cavity qed materials seeks to modify the properties of bulk materials by coupling them to an electromagnetic cavity at equilibrium. When the material is, e.g., composed of magnetic dipoles, the resulting system is described by a generalized Dicke model. Under certain conditions, the cavity modes can be traced out, leaving a spin Hamiltonian with cavity-mediated (effective)...

39. Encodings of binary variables for efficient use in a quantum computer

Márcio Taddei (ICFO - The Institute of Photonic Sciences)

01/06/2023, 12:00

Talk

Quantum computers in the NISQ era (noisy, intermediate-scale, quantum) still offer a relatively small amount of qubits. The largest quantum computers so far, dedicated to binary optimization, do not surpass a few thousands qubits. We nevertheless are willing and able to probe such computers in real-life tasks with their high demand in number of variables to optimize over.
We tackle a binary...

35. Quantum circuits for quantum walks with position-dependent coin operator

Armando Perez (Departamento de Física Teórica & IFIC. Universidad de Valencia/CSIC)

01/06/2023, 12:20

Talk

Quantum walks (QWs) play an important role in quantum computing. On the one hand, some algoritmical problems can be recast as a QW. On the other hand, many physical phenomena can be simulated with the help of a QW. Here we concentrate on discrete-time QWs, and we discuss quantum circuits that can implement discrete-time quantum walks having an arbitrary position-dependent coin operator [1]....

69. Parallelizing quantum algorithms with classical communication.

Constantino Rodriguez Ramos (CESGA)

01/06/2023, 12:40

Talk

Hybrid quantum-classical algorithms emerge as one promising approach to improve the performance of current quantum computers. In this work, we consider the method to execute general quantum algorithms on two different QPUs connected via classical communication. The optimal protocol for such computation consists of two steps: First, a quasi-probabilistic simulation scheme generates the required...