A family of double-quantum excitation schemes is described for the solution nuclear magnetic resonance (NMR) of near-equivalent spin-1/2 pairs. These new methods exploit the spinor behaviour of 2-level systems, whose signature is the change of sign of a quantum state upon a $2π$ rotation. The spinor behaviour is used to manipulate the phases of single-quantum coherences, in order to prepare a double-quantum precursor state which is rapidly converted into double-quantum coherence by a straightforward $π/2$ rotation. One set of spinor-based methods exploits symmetry-based pulse sequences, while the other set exploits SLIC (spin-lock-induced crossing), in which the nutation frequency under a resonant radiofrequency field is matched to the spin-spin coupling. A variant of SLIC is introduced which is well-compensated for deviations in the radiofrequency field amplitude. The methods are demonstrated by performing double-quantum-filtered $^{19}$ F NMR on a molecular system containing a pair of diastereotopic $^{19}$ F nuclei. The new methods are compared with existing techniques.A family of double-quantum excitation schemes is described for the solution nuclear magnetic resonance (NMR) of near-equivalent spin-1/2 pairs. These new methods exploit the spinor behaviour of 2-level systems, whose signature is the change of sign of a quantum state upon a $2π$ rotation. The spinor behaviour is used to manipulate the phases of single-quantum coherences, in order to prepare a double-quantum precursor state which is rapidly converted into double-quantum coherence by a straightforward $π/2$ rotation. One set of spinor-based methods exploits symmetry-based pulse sequences, while the other set exploits SLIC (spin-lock-induced crossing), in which the nutation frequency under a resonant radiofrequency field is matched to the spin-spin coupling. A variant of SLIC is introduced which is well-compensated for deviations in the radiofrequency field amplitude. The methods are demonstrated by performing double-quantum-filtered $^{19}$F NMR on a molecular system containing a pair of diastereotopic $^{19}$F nuclei. The new methods are compared with existing techniques.

quant-pharXiv:2602.08157Feb 10, 2026

Tunnelling-Induced Transient Gain in an Asymmetric Double Quantum Well

Xu Wei-Hua, Wu Jin-Hui, Jin-Yue Gao

We investigate the transient behaviour of a weak probe in asymmetric double quantum well structures, where two excited states are coupled by resonant tunnelling through a thin barrier in a three-level system of electronic subbands. There is no external coherent coupling field applied, and we find that probe gain can be achieved during the transient process, which is induced by the coherent coupling of the upper states via the resonant tunnelling. We show that the transient behaviour of the probe depends on the coupling strength and the dephasing rate and can be tuned by changing the width of the tunnelling barrier.We investigate the transient behaviour of a weak probe in asymmetric double quantum well structures, where two excited states are coupled by resonant tunnelling through a thin barrier in a three-level system of electronic subbands. There is no external coherent coupling field applied, and we find that probe gain can be achieved during the transient process, which is induced by the coherent coupling of the upper states via the resonant tunnelling. We show that the transient behaviour of the probe depends on the coupling strength and the dephasing rate and can be tuned by changing the width of the tunnelling barrier.

Chinese Physics LettersMay 1, 20046 citations

Double-quantum nutations in a two-level spin system

R. Boscaino, F. M. Gelardi, G. Messina

Solid State CommunicationsJun 1, 19837 citations

Quantum Phase Transition in the Spin Boson Model

Serge Florens, D. Venturelli, R. Narayanan

arXiv:1106.2654Lecture notes in physicsJan 1, 201016 citations

Theoretical Considerations of the Three-Level Maser Detector for the Far-Infrared

Kōichi Shimoda

In the case when the pumping transition in a three-level system of a molecule does not exactly coincide with the output frequency of a maser oscillator, four different types of operation at off-resonance of the three-level maser detector are discussed. At first the use of pressure broadening is considered; secondly a method which observes the double-quantum transition and thirdly the other method which measures a change in population caused by the double-quantum pumping are considered, and finally the level shift due to the far-infrared input is considered. It is found that the third method of double-quantum pumping in which three waves are involved is the most sensitive. The minimum detectable power of order 10-6W/cm2 with the resolving time of about 10-6s is expected in detecting the maser output at the far-infrared which differs from the resonant frequency of the detector by as large as 10 GHz.In the case when the pumping transition in a three-level system of a molecule does not exactly coincide with the output frequency of a maser oscillator, four different types of operation at off-resonance of the three-level maser detector are discussed. At first the use of pressure broadening is considered; secondly a method which observes the double-quantum transition and thirdly the other method which measures a change in population caused by the double-quantum pumping are considered, and finally the level shift due to the far-infrared input is considered. It is found that the third method of double-quantum pumping in which three waves are involved is the most sensitive. The minimum detectable power of order 10-6W/cm2 with the resolving time of about 10-6s is expected in detecting the maser output at the far-infrared which differs from the resonant frequency of the detector by as large as 10 GHz.

Japanese Journal of Applied PhysicsMay 1, 19677 citations

2π

rotation. The spinor behaviour is used to manipulate the phases of single-quantum coherences, in order to prepare a double-quantum precursor state which is rapidly converted into double-quantum coherence by a straightforward

π/2

rotation. One set of spinor-based methods exploits symmetry-based pulse sequences, while the other set exploits SLIC (spin-lock-induced crossing), in which the nutation frequency under a resonant radiofrequency field is matched to the spin-spin coupling. A variant of SLIC is introduced which is well-compensated for deviations in the radiofrequency field amplitude. The methods are demonstrated by performing double-quantum-filtered

^{19}

F NMR on a molecular system containing a pair of diastereotopic

^{19}

F nuclei. The new methods are compared with existing techniques.