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Title: Strategic Codes: The Universal Spatio-Temporal Framework for Quantum Error-Correction
Date/Time: 17-Jul, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15
The emerging paradigm of dynamical quantum error-correcting codes (QECC) has led to a plethora of error-correction schemes that uses a sequence of operations evolving how quantum information is spatially encoded over time, as opposed to a fixed spatial many-body encoding in conventional static QECCs. Substantial progress in dynamical QECC research has led to more resource-efficient codes with fundamentally interesting features.However, an understanding of the extent of how error-correction can be performed utilizing both space and time domains is limited due to the lack of a unified framework. We address this gap by proposing the ``strategic code\'\' framework, the most general QECC framework encompassing all existing codes and any physically plausible codes to be discovered, as well as capturing its interplay with the most general type of noise environment with spatio-temporal correlations. The framework uses an ``interrogator\'\' device, which allows a code to perform the most general quantum process that adaptively interacts with the noise environment over multiple time-steps, both of which are represented in the quantum combs formalism. Using the framework, we establish necessary and sufficient error-correction conditions for a strategic code under a general non-markovian error model in two forms: algebraic and information-theoretic, which include analogous known static QECC conditions as a special case. We also provide an optimization problem to systematically obtain a strategic code that recovers quantum information up to a desired fidelity under a given noise model with arbitrary correlations.Arxiv preprint: https://arxiv.org/abs/2405.17567
Title: Demonstrating quantum phase estimation with error detection code on a trapped-ion computer
Date/Time: 24-Jul, 12:00PM
Venue: Level 3 Seminar Room, S15-03-15
Quantum phase estimation (QPE) serves as a building block of many different quantum algorithms and finds important applications in computational chemistry problems. Despite the rapid development of quantum hardware, experimental demonstration of QPE for chemistry problems remains challenging due to its large circuit depth and the lack of quantum resources to protect the hardware from noise with fully fault-tolerant protocols. In the present work, we take a step towards fault-tolerant quantum computing by demonstrating a QPE algorithm on a Quantinuum trapped-ion computer with a [[n+2, n, 2]] quantum error detection code carefully tailored to the hardware capabilities such as mid-circuit measurement, qubit reuse, and conditional logic. As a simple quantum chemistry example, we take a hydrogen molecule represented by a two-qubit Hamiltonian and estimate its ground state energy using our novel QPE protocol.
Title: To mitigate or not to mitigate: will quantum error mitigation make NISQ devices useful?
Date/Time: 25-Jul, 03:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15
Mitigating noise in a quantum circuit/device without knowing the nature of the noise or the expected output of the ideal circuit seems like an unrealistic challenge. Yet, Quantum Error Mitigation (QEM) encompasses a range of postprocessing techniques that achieve precisely that. This magic comes at a price of extra runtime for reducing the statistcal sampling uncertainty. These days, QEM is utilized in the vast majority of quantum computer experiments. While it was orginally designed as an intermediate solution until quantum error correction code technology matures, QEM also holds promise for long-term use in alleviating the substantial hardware overhead associated with error correction. In this talk we present our pulse-based Adaptive KIK technique [1] for mitigating incoherent errors (Markovian noise) and also introduce the Pseudo Twirling protocol for mitigating coherernt errors (crosstalks and non-Markovian noise). Finally we show that for high fidelity circuits, error mitigation should already be used in the gate calibration processes. The talk will contain both theory and experimental results from the IBMQ and AQT platforms.[1] I. Henao, J. P. Santos and R. Uzdin, npj Quantum Information 1, 120 (2023)
Title: Optical Fibre Sensing for Seismic Events
Date/Time: 26-Jul, 02:00PM
Venue: CQT Level 3 Conference Room, S15-03-17
Apart from distributed acoustic sensing, deployed optical fibers can also be used as integral phase sensors to detect very small integral strains. This is potentially useful for detecting seismic events. We present preliminary phase sensing results from 1 km to 20 km fiber sensors.