Publications by authors named "A Retzker"
Decoherence and imperfect control are crucial challenges for quantum technologies. Common protection strategies rely on noise temporal autocorrelation, which is not optimal if other correlations are present. We develop and demonstrate experimentally a strategy that uses the cross-correlation of two noise sources.
View Article and Find Full Text PDFDiffusion noise represents a major constraint to successful liquid state nano-NMR spectroscopy. Using the Fisher information as a faithful measure, we theoretically calculate and experimentally show that phase sensitive protocols are superior in most experimental scenarios, as they maximize information extraction from correlations in the sample. We derive the optimal experimental parameters for quantum heterodyne detection (Qdyne) and present the most accurate statistically polarized nano-NMR Qdyne detection experiments to date, leading the way to resolve chemical shifts and J couplings at the nanoscale.
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- This research presents a technique using parahydrogen-induced polarization (PHIP) to enhance the observation of carbon-labeled metabolites through magnetic resonance imaging (MRI) for real-time monitoring inside the body.
- The method involves transferring parahydrogen-derived singlet order into carbon magnetization using adiabatic radio frequency sweeps at very low magnetic fields, resulting in substantial increases in nuclear spin polarization, sometimes exceeding 60%.
- Additionally, a new approach involving site-selective deuteration is introduced to improve the efficiency of polarization transfer by integrating deuterium into the molecular structure, minimizing relaxation effects from closely coupled nuclei.
The impact of measurement imperfections on quantum metrology protocols has not been approached in a systematic manner so far. In this work, we tackle this issue by generalising firstly the notion of quantum Fisher information to account for noisy detection, and propose tractable methods allowing for its approximate evaluation. We then show that in canonical scenarios involving N probes with local measurements undergoing readout noise, the optimal sensitivity depends crucially on the control operations allowed to counterbalance the measurement imperfections-with global control operations, the ideal sensitivity (e.
View Article and Find Full Text PDFDiffusion broadening of spectral lines is the main limitation to frequency resolution in non-polarized liquid state nano-NMR. This problem arises from the limited amount of information that can be extracted from the signal before losing coherence. For liquid state NMR as with most generic sensing experiments, the signal is thought to decay exponentially, severely limiting resolution.
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