Research Studentships for Master or Integrated Master students - (BL19/2024_IST-ID)

11 Mar 2024
Job Information

Organisation/Company

Associação do Instituto Superior Técnico para a Investigação e Desenvolvimento _IST-ID

Department

DRH

Research Field

Physics » Other

Researcher Profile

First Stage Researcher (R1)

Country

Portugal

Application Deadline

25 Mar 2024 - 23:59 (Europe/Lisbon)

Type of Contract

Not Applicable

Job Status

Not Applicable

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Reference Number

QuantERA/0003/2021

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

Applications are open for four (4) Research Studentships, within the framework of project(1801P.01178.1.01) DQUANT - QuantERA/0003/2021 - IST-ID financed by national funds through FCT/MCTES (PIDDAC

Workplan Studenship 1: Title:  Universal Properties of Non-Markovian Dissipative Quantum Systems

 

Description: 

 

Quantum systems with many particles may exhibit such complex Hamiltonians that they behave in several aspects like large random matrices. Due to this intriguing observation, random matrix models have been used since the 70`s to study the statistical properties of isolated chaotic quantum systems. Recently, this approach has been extended to quantum systems coupled to an external environment that induces dissipation and decoherence. This is possible when the characteristic memory times of the environment are significantly smaller than those of the system. Such environments are said to be Markovian (i.e., memoryless) and allow the system’s evolution to be described by a Liouvillian operator of the Lindblad type. Applying random matrix theory to Lindbladians we were able to obtain universal properties of chaotic open quantum systems. Since then, random Lindbladians have been shown to accurately describe the noise of the IBM quantum computing platform. While the results for Markovian systems are quite encouraging, in many physically relevant cases the Markovian approximation does not hold. The goal of this thesis is to extend the study of spectral and steady-state properties of random Liouvillians to non-Markovian environments. To keep the problem treatable, we will restrict or approach to quadratic fermionic models where a closed form for the evolution, after integrating over the environment degrees of freedom, can be derive using non-equilibrium Green`s functions. We shall use this approach to reconstruct the Liouvillian and study the statistical properties once the system Hamiltonian and the system-environment couplings are sampled over appropriate random matrix ensembles.

 

Workplan Studenship 2: Title:  Liouvillian Tomography in Noisy Intermediate-scale Quantum Computers         

 

Description: 

 

The current phase of quantum computing is often described as the "noisy intermediate-scale quantum" (NISQ) era. Up to now, although quantum processors may contain up to 1000 qubits, they have not reached the level of advancement required for fault-tolerant operations or to achieve undisputable quantum supremacy. NISQ processors are very sensitive to their environment, making them prone to quantum decoherence and dissipation. In this context, it is crucial to understand how the environment interacts with the multi-qubit system, and to accurately characterize the processes of dissipation and decoherence. This understanding is essential for making systematic improvements to NISQ devices.Traditional metrics for dissipation and decoherence, such as T1 and T2, offer only limited insights. More recently developed techniques like tomography processes and randomized benchmarking provide more information but still fall short of fully characterizing dynamic dissipative channels involving multiple qubits. Notably, a significant advancement has been made with the introduction of a method called Lindblad Tomography. This method, built upon standard process tomography, can place constraints on Markovian models and identify sources of crosstalk in quantum processors. However, it assumes a time-independent Liouvillian of the Lindblad form which is still very restrictive.

 

In this project, our goal is to comprehensively characterize the time-dependent Liouvillian map of a few-qubit quantum processor under the influence of the elementary pulses used to perform quantum gates. We will build upon a recent quantum map-retrieving algorithm inspired by machine learning techniques. Our approach will involve extracting the complete Liouvillian generator and identifying the Hamiltonian and, potentially, non-Markovian jump operators responsible for dissipative quantum dynamics.

The specific objectives of this project include:

1. Implementing a time-resolved quantum map-retrieving algorithm.

2. Recovering the time-local Liouvillian generator through a discrete-time approximation method.

3. Validating the results using synthetic data that simulates non-Markovian environments.

4. Estimating errors and confidence levels associated with the retrieved map.

5. Applying the developed technique to NISQ devices to systematically characterize dissipative channels and unitary errors.

 

The outcomes of this work hold direct significance for the characterization of NISQ platforms, pinpointing sources of decoherence, dissipation, and unitary errors. Identifying the physical processes behind these sources of errors is a crucial step toward designing more robust quantum processors.

 

Workplan Studenship 3: Title:  Assessing Quantum Computers' Performance in the NISQ Era

 

Description: 

 

Achieving undeniable quantum supremacy requires the precise manipulation of many high-quality qubits. Whether the endeavour of building such a quantum computer is possible remains a central question with profound implications for both physics and technology. Currently, we are living in the "noisy intermediate-scale quantum" (NISQ) era, characterized by small and imperfect quantum processors. Our immediate challenge is to improve their quality and scalability. To address this challenge, we need tools that facilitate the comparison of various strategies and architectures for quantum computer construction. This task is complex, as numerous factors, such as the number of qubits, connectivity, quantum gates, and compatibility with classical software, influence a quantum computer`s performance.Quantum Volume (QV) serves as a comprehensive performance metric for quantum computers. It represents the largest random square quantum circuit (i.e. with the same number of qubits as layers) that can be run with reliable results. In this way, it assesses a quantum computer`s capability without delving into its specific details. Computing QV involves determining the average over random circuits of the fidelity between an ideal state (resulting from a faultless computer) and an imperfect state (resulting from a faulty one).This project aims to gain a deeper understanding of QV and explore how it depends on factors like expressibility (the range of achievable unitaries in a circuit), connectivity, and gate size. This analysis will help us decide when QV is suitable and when additional refinements are necessary for meaningful comparisons of quantum processors.

 

The specific objectives of this project are as follows:

1. Generate random circuits with different connectivity patterns.

2. Create non-generic random circuits that mimic the behavior of free-fermion systems with different connectivities.

3. Analyze the dependence of average fidelity on the number of qubits, circuit depth, and error rate.

4. Develop theoretical predictions based on Random Matrix Theory.

 

The project stands out for the following distinctive characteristics:

1. Identifying promising architectures for building larger and better quantum computers.

2. Paving the way for extending measures of the performance of quantum computers to realistic scenarios.

3. Embracing a multidisciplinary perspective, as random circuits have gained significance across various fields of theoretical physics, including quantum chaos, quantum hydrodynamics, and black-hole physics.

 

 

Workplan Studenship 4: Title:  Bias-driven non-equilibrium phase transitions

 

Description: 

 

Although equilibrium quantum phase transitions have been extensively explored, their non-equilibrium counterparts still present numerous unresolved questions. Previous investigations into non-equilibrium field theories have revealed that non-equilibrium drives can significantly alter the nature of the transition, introduce heating phenomena, or establish universal classes without classical analogs. Nonetheless, a comprehensive and systematic understanding is currently lacking.

 

This project aims to address non-equilibrium phase transitions using a simplified quantum transport setup, shedding light on their properties and identifying observable signatures in transport experiments. Specifically, our focus is on developing a theoretical model for the quantum dot`s degrees of freedom as it undergoes a quantum phase transition under the influence of a bias voltage.

The specific objectives of this project include:

- Developing a suitable model for describing the quantum dot`s degrees of freedom.

- Constructing the non-equilibrium phase diagram.

- Deriving the effective field theory applicable near the non-equilibrium transition.

- Analyzing the impact of critical fluctuations on current and current noise.

Duration: The research fellowship(s) will have the duration of 3 months. It’s expected to begin as soon as possible and may not be renewed.

It is mandatory to formalize applications with the submission of the following documents: i) B1 Form – Fellowship application (https://ist-id.pt/concursos/bolsas/  ); ii) Curriculum Vitae; iii)academic degree certificate, where applicable; iv) proof of enrollment at an academic degree course; v) motivation letter.

Applications must be submitted to the email: [email protected]

Requirements

Research Field

Physics » Other

Education Level

Undergraduate

Skills/Qualifications

Admission Requirements: To be enrolled at an integrated master or a master.

Additional Information
Benefits

Monthly maintenance allowance: According to the values for Research Fellowships awarded by FCT in Portugal (https://www.fct.pt/wp-content/uploads/2024/02/Tabela-de-Valores-SMM_atualizacao-2024.pdf ), the amount of the monthly maintenance allowance is €990,98, being the payment method by Wire Transfer.

Eligibility criteria

Admission Requirements: To be enrolled at an integrated master or a master.

Selection process

Selection methods: The selection methods will be the following: The selection methods to be used will be the following: curricular assessment and previous experience, with the respective valuation of 60 and 40 out of a total of 100 values.

Composition of the selection Jury: João Seixas, Pedro Sacramento, Pedro Ribeiro.

Announcement/ notification of the results: The final evaluation results will be communicated to all applicants by email.

Deadlines and procedures of complaint and appeal . A complaint may be lodged from the final decision within 15 working days, or an appeal to the Executive Board of IST-ID within 30 working days, both counted from the respective notification

Additional comments

Legislation and Regulations: Statute of Scientific Research Fellow, approved by Law nr. 40/2004, of August 18, as worded by Decree-Law nr. 123/2019, of August 28; FCT Regulation for Research Studentships and Fellowships, available on https://www.fct.pt/apoios/bolsas/docs/RegulamentoBolsasFCT2019.pdf and https://dre.pt/application/file/a/127230968 .

Workplace The work will be developed at CeFEMA, of Instituto Superior Técnico under the scientific supervision of Professor Pedro Ribeiro.

Website for additional job details

https://ist-id.pt/concursos/bolsas/

Work Location(s)

Number of offers available

4

Company/Institute

IST-ID

Country

Portugal

Geofield

Where to apply

E-mail

[email protected]

Contact

City

Lisbon

Website

http://ist-id.pt/

Street

Av. Rovisco Pais

Postal Code

1049-001 Lisboa

STATUS: EXPIRED