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In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
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NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of...
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Fabrizio Berritta1, Torbjørn Rasmussen2, Jan A Krzywda3

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This study introduces a real-time quantum control protocol for qubits, using dynamic waveform generation to stabilize performance against environmental noise. The method optimizes qubit operations by estimating and correcting Hamiltonian parameter fluctuations in real time.

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Area of Science:

  • Quantum Computing
  • Quantum Control
  • Solid-State Physics

Background:

  • Qubit control is challenged by environmental noise affecting Hamiltonian parameters.
  • Adapting to these dynamic changes is crucial for stable quantum computations.

Purpose of the Study:

  • To demonstrate a real-time control protocol for a two-electron singlet-triplet qubit.
  • To dynamically stabilize and optimize qubit performance against fluctuating Hamiltonian parameters.

Main Methods:

  • Leveraging single-shot readout classification and dynamic waveform generation.
  • Utilizing field-programmable gate array (FPGA) for real-time Hamiltonian estimation.
  • Estimating Overhauser field gradient and exchange interaction for dynamic correction.

Main Results:

  • Achieved real-time estimation and correction of fluctuating qubit parameters.
  • Enabled controlled Overhauser-driven spin rotations without external magnets.
  • Extended coherence of Hadamard rotations by correcting for qubit axis fluctuations.

Conclusions:

  • Feedback-based control is essential for enhancing quantum device performance and stability.
  • The demonstrated protocol effectively mitigates quasistatic noise in qubits.
  • This approach offers a pathway to more robust quantum information processing.