© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Decoherence of superposition states in trapped ions

Hermann Uys, Michael J. Biercuk, Aaron P. van Devender, C. Ospelkaus, D. Meiser, Roee Ozeri, J. J. Bollinger

Published Sep 1, 2010• 0 citations

Abstract

We investigate the decoherence of superpositions of hyperfine states of Be ions due to spontaneous scattering of off-resonant light. We find that, contrary to conventional wisdom, elastic Rayleigh scattering can have majour contributions to decoherence when compared to the effect of inelastic Raman scattering. 1. Summary Minimizing the effects of decoherence is a central challenge in many quantum physics experiments. In the case of ion trap quantum computing [1] a majour contribution to decoherence comes from the off-resonant scattering of the controlling light beams. It is often assumed that the decoherence process is dominated by in-elastic Raman scattering, since in that case the scattered photon has a different frequency from the incoming photon, and consequently carries with it information regarding the internal state of the ion [2, 3]. This leads to decoherence of that internal state. On the otherhand since Rayleigh scattering does not carry this information it is assumed to not lead to comparable decoherence. Here we show that under certain circumstances the Rayleigh scattering can dominate the ecoherence process even at large detunings from the excited state levels. We find excellent agreement between a masters theory approach and experimental measurements. Figure 1: Comparison of decoherence rates as a function of detuning from the Be cycling transition. Squares experiment, Blue/Red line full masters equation theory, Cyan line incomplete model sometimes used in literature. 2. References [1] D.J. Wineland, et al., Phil. Trans. R. Soc. Lond. A 361, 1349 (2003). [2] R. Ozeri, et al., Phys. Rev. A 75, 042329 (2007). [3] R. Ozeri, et al., Phys. Rev. Lett. 95, 030402 (2005).

Related papers

Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

Roee Ozeri, C. Langer, John D. Jost +11 more

The coherence of a hyperfine-state superposition of a trapped 9Be+ ion in the presence of off-resonant light is studied experimentally. It is shown that Rayleigh elastic scattering of photons that does not change state populations also does not affect coherence. We observe coherence times that exceed the average scattering time of 19 photons which is determined from measured Stark shifts. This result implies that, with sufficient control over its parameters, laser light can be used to manipulate hyperfine-state superpositions with very little decoherence.

arXiv:quant-ph/0502063•Physical Review Letters•Jul 14, 2005•112 citations

Decoherence due to Elastic Rayleigh Scattering

Hermann Uys, Michael J. Biercuk, Aaron P. VanDevender +4 more

We present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of light off resonant with higher lying excited states. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the dominant source of decoherence, contrary to previous discussions in the literature. We show that the elastic-scattering decoherence rate of a two-level system is given by the square of the difference between the elastic-scattering amplitudes for the two levels, and that for certain detunings of the light, the amplitudes can interfere constructively even when the elastic-scattering rates from the two levels are equal. We confirm this prediction through calculations and measurements of the total decoherence rate for a superposition of the valence electron spin levels in the ground state of 9Be+ in a 4.5 T magnetic field.

arXiv:1007.2661•Physical Review Letters•Nov 8, 2010•99 citations

Decoherence in ion traps

Sara Schneider, Gerard J Milburn

Summary form only given.To model the decoherence in ion traps resulting from laser intensity and phase fluctuations, we assume that the stochastic processes involved are white noise processes, which enables us to give a simple master equation description of this source of decoherence. We discuss the effects those fluctuations have on gate operations in ion-trap quantum computation and briefly address possible detection and error correction mechanisms. The master equation is then averaged over the noise and is sufficient to describe the results of experiments that probe the oscillations in the electronic populations as energy is exchanged between the internal and electronic motion. We get solutions for the probability of the ion to be in the ground state for both intensity and phase fluctuations. Our results predict that the decoherence rate resulting from intensity fluctuations will depend on the vibrational quantum number in different ways depending on which vibrational excitation sideband is used. So the dependence of the decoherence rate for the second red sideband depends quadratically on the vibrational energy state |n> the ion is prepared in, whereas for the first sideband, this effect is linear in n. Due to this result, the second red (or any higher-order) sideband is a better choice for testing the dependence of decoherence on the excitation in the vibrational state experimentally than just the first-order sideband. Because those fluctuations in the exciting laser pulse are not the only source of decoherence, we briefly discuss fluctuations in the trap potential itself. These fluctuations lead to a wobbling trap center point, and we discuss the effects due to them.

Conference on Lasers and Electro-Optics•Nov 27, 2002•0 citations

Light scattering from laser-trapped atoms

Robert A. Cline, Joseph D. Miller, M. R. Matthews +1 more

We study a novel property of light scattering by Rb atoms confined in a far off-resonance optical dipole force trap. The trapping laser wavelength varies from 780 nm to 860 nm and its intensity is about 1 MW/cm{sup 2}. Spontaneous Raman scattering of photons from the trapping laser can change the ground-state hyperfine quantum number F of the atoms. We observe the relaxation time by measuring the population of the F=3 level after optically pumping the atoms into the F=2 level. Spontaneous photon scatter rates as low as 10{sup 3} s{sup -1} have been observed, corresponding to recoil heating rates below 1 mK/s. For detuning from resonance {Delta} greater than the excited-state fine-structure splitting the total scatter rate, including Rayleigh scattering, decreases as {Delta}{sup 2} while the spontaneous Raman scatter rate decreases as {Delta}{sup 4}. This is due to interference between the Raman scattering amplitudes from the two excited-state fine-structure levels in the Kramers-Heisenberg formula. Because Rayleigh scattering dominates, the atoms` F and M{sub F} quantum numbers are preserved even after many scattering events. This makes far off-resonance optical traps ideal for studies of state-selective collisions and collective phenomena.

Bulletin of the American Physical Society•May 1, 1993•0 citations

Decoherence in ion traps due to laser intensity and phase fluctuations

Sara Schneider, Gerard J Milburn

We consider one source of decoherence for a single trapped ion due to intensity and phase fluctuations in the exciting laser pulses. For simplicity we assume that the stochastic processes involved are white noise processes, which enables us to give a simple master equation description of this source of decoherence. This master equation is averaged over the noise, and is sufficient to describe the results of experiments that probe the oscillations in the electronic populations as energy is exchanged between the internal and electronic motion. Our results are in good qualitative agreement with recent experiments and predict that the decoherence rate will depend on vibrational quantum number in different ways depending on which vibrational excitation sideband is used.

arXiv:quant-ph/9710044•Physical Review A•May 1, 1998•109 citations

Optimal Phase Sensing in Trapped Ions with One-Axis-Twisting Hamiltonian

Wenchao Ge

Trapped ions are a well-developed platform to estimate a phase imprinted on their internal quantum states. However, an optimal quantum-enhanced protocol to robustly read out the phase under practical conditions in trapped ions has not been explored. Here, we study such a protocol via interaction-based readout in trapped ions with a one-axis twisting Hamiltonian considering a practical experimental situation. We start from a more fundamental spin-motion coupling in trapped ions, mediated by laser beams, to explore the dependence of the phase sensitivity on the specific interaction. We evaluate the decoherence effects of both Rayleigh scattering and Raman scattering due to spontaneous emission of the laser beams. We find that the phase sensitivity is mostly robust to decoherence when the system is operated in the so-called “squeezing regime”. Interestingly, we find that larger Raman scattering leads to slightly better phase sensitivity for a fixed total decoherence rate in this regime. We further analyze the effects of the frequency fluctuations from the center-of-mass (COM) mode in the phase sensing protocol and find that they are negligible under practical experimental parameters. Our work lays the theoretical foundation for estimating a collective phase rotation using entangled spin states in trapped ions.

Fluctuation and Noise Letters•Jan 10, 2026•0 citations

We investigate the decoherence of superpositions of hyperfine states of Be ions due to spontaneous scattering of off-resonant light. We find that, contrary to conventional wisdom, elastic Rayleigh scattering can have majour contributions to decoherence when compared to the effect of inelastic Raman scattering. 1. Summary Minimizing the effects of decoherence is a central challenge in many quantum physics experiments. In the case of ion trap quantum computing [1] a majour contribution to decoherence comes from the off-resonant scattering of the controlling light beams. It is often assumed that the decoherence process is dominated by in-elastic Raman scattering, since in that case the scattered photon has a different frequency from the incoming photon, and consequently carries with it information regarding the internal state of the ion [2, 3]. This leads to decoherence of that internal state. On the otherhand since Rayleigh scattering does not carry this information it is assumed to not lead to comparable decoherence. Here we show that under certain circumstances the Rayleigh scattering can dominate the ecoherence process even at large detunings from the excited state levels. We find excellent agreement between a masters theory approach and experimental measurements. Figure 1: Comparison of decoherence rates as a function of detuning from the Be cycling transition. Squares experiment, Blue/Red line full masters equation theory, Cyan line incomplete model sometimes used in literature. 2. References [1] D.J. Wineland, et al., Phil. Trans. R. Soc. Lond. A 361, 1349 (2003). [2] R. Ozeri, et al., Phys. Rev. A 75, 042329 (2007). [3] R. Ozeri, et al., Phys. Rev. Lett. 95, 030402 (2005).

The coherence of a hyperfine-state superposition of a trapped 9Be+ ion in the presence of off-resonant light is studied experimentally. It is shown that Rayleigh elastic scattering of photons that does not change state populations also does not affect coherence. We observe coherence times that exceed the average scattering time of 19 photons which is determined from measured Stark shifts. This result implies that, with sufficient control over its parameters, laser light can be used to manipulate hyperfine-state superpositions with very little decoherence.

We present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of light off resonant with higher lying excited states. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the dominant source of decoherence, contrary to previous discussions in the literature. We show that the elastic-scattering decoherence rate of a two-level system is given by the square of the difference between the elastic-scattering amplitudes for the two levels, and that for certain detunings of the light, the amplitudes can interfere constructively even when the elastic-scattering rates from the two levels are equal. We confirm this prediction through calculations and measurements of the total decoherence rate for a superposition of the valence electron spin levels in the ground state of 9Be+ in a 4.5 T magnetic field.

Summary form only given.To model the decoherence in ion traps resulting from laser intensity and phase fluctuations, we assume that the stochastic processes involved are white noise processes, which enables us to give a simple master equation description of this source of decoherence. We discuss the effects those fluctuations have on gate operations in ion-trap quantum computation and briefly address possible detection and error correction mechanisms. The master equation is then averaged over the noise and is sufficient to describe the results of experiments that probe the oscillations in the electronic populations as energy is exchanged between the internal and electronic motion. We get solutions for the probability of the ion to be in the ground state for both intensity and phase fluctuations. Our results predict that the decoherence rate resulting from intensity fluctuations will depend on the vibrational quantum number in different ways depending on which vibrational excitation sideband is used. So the dependence of the decoherence rate for the second red sideband depends quadratically on the vibrational energy state |n> the ion is prepared in, whereas for the first sideband, this effect is linear in n. Due to this result, the second red (or any higher-order) sideband is a better choice for testing the dependence of decoherence on the excitation in the vibrational state experimentally than just the first-order sideband. Because those fluctuations in the exciting laser pulse are not the only source of decoherence, we briefly discuss fluctuations in the trap potential itself. These fluctuations lead to a wobbling trap center point, and we discuss the effects due to them.

We study a novel property of light scattering by Rb atoms confined in a far off-resonance optical dipole force trap. The trapping laser wavelength varies from 780 nm to 860 nm and its intensity is about 1 MW/cm{sup 2}. Spontaneous Raman scattering of photons from the trapping laser can change the ground-state hyperfine quantum number F of the atoms. We observe the relaxation time by measuring the population of the F=3 level after optically pumping the atoms into the F=2 level. Spontaneous photon scatter rates as low as 10{sup 3} s{sup -1} have been observed, corresponding to recoil heating rates below 1 mK/s. For detuning from resonance {Delta} greater than the excited-state fine-structure splitting the total scatter rate, including Rayleigh scattering, decreases as {Delta}{sup 2} while the spontaneous Raman scatter rate decreases as {Delta}{sup 4}. This is due to interference between the Raman scattering amplitudes from the two excited-state fine-structure levels in the Kramers-Heisenberg formula. Because Rayleigh scattering dominates, the atoms` F and M{sub F} quantum numbers are preserved even after many scattering events. This makes far off-resonance optical traps ideal for studies of state-selective collisions and collective phenomena.

We consider one source of decoherence for a single trapped ion due to intensity and phase fluctuations in the exciting laser pulses. For simplicity we assume that the stochastic processes involved are white noise processes, which enables us to give a simple master equation description of this source of decoherence. This master equation is averaged over the noise, and is sufficient to describe the results of experiments that probe the oscillations in the electronic populations as energy is exchanged between the internal and electronic motion. Our results are in good qualitative agreement with recent experiments and predict that the decoherence rate will depend on vibrational quantum number in different ways depending on which vibrational excitation sideband is used.

Trapped ions are a well-developed platform to estimate a phase imprinted on their internal quantum states. However, an optimal quantum-enhanced protocol to robustly read out the phase under practical conditions in trapped ions has not been explored. Here, we study such a protocol via interaction-based readout in trapped ions with a one-axis twisting Hamiltonian considering a practical experimental situation. We start from a more fundamental spin-motion coupling in trapped ions, mediated by laser beams, to explore the dependence of the phase sensitivity on the specific interaction. We evaluate the decoherence effects of both Rayleigh scattering and Raman scattering due to spontaneous emission of the laser beams. We find that the phase sensitivity is mostly robust to decoherence when the system is operated in the so-called “squeezing regime”. Interestingly, we find that larger Raman scattering leads to slightly better phase sensitivity for a fixed total decoherence rate in this regime. We further analyze the effects of the frequency fluctuations from the center-of-mass (COM) mode in the phase sensing protocol and find that they are negligible under practical experimental parameters. Our work lays the theoretical foundation for estimating a collective phase rotation using entangled spin states in trapped ions.