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Understanding atomic interactions in an optical lattice clock and using them to study many-body physics

Michael Bishof

Published Jan 1, 2014• 0 citations
OpenAlex

Abstract

Strontium optical lattice clocks at JILA recently demonstrated record-high accuracy and stability. These advances were enabled by an ultrastable laser with fractional frequency stability of 1x10-16 at 1 second. This laser allows us to study systematic shifts of the 1S0 to 3P0 clock transition with unprecedented precision. Density-dependent frequency shifts represent an unavoidable perturbation for clocks based on many atoms. Our studies of atomic interactions in an optical lattice clock system uncover the nature of these interactions and reveal important many-body atomic correlation effects in this open quantum system. By extending our measurements to all ten nuclear-spin sublevels of the clock states, we observe the first direct evidence of SU(N) symmetric interactions in alkaline earth(-like) atoms. Using the techniques we developed in these studies, we also demonstrate a novel technique for measuring the frequency noise spectrum of an ultrastable laser. We discuss designs for the future direction of our experiment which will place 87Sr atoms within a high finesse cavity that is resonant on the 1S0 to 3P1 transition. We will use this system to study collective effects in cavity quantum electrodynamics. Most notably, strong atom-cavity coupling can enhance the spectroscopic sensitivity of our clock by creating spin-squeezed states via quantum non-demolition measurements. As a precursor to future work studying cavity-mediated collective behavior, we use the unique atomic structure of 88Sr to investigate free-space retarded dipolar coupling in an optically thick sample of atoms.

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Operating a 87 Sr optical lattice clock with high precision and at high density

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We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at the 10-(16) fractional frequency level. An upgraded laser system has recently been constructed in our lab which may allow the JILA Sr standard to reach the standard quantum measurement limit and achieve record levels of stability. To take full advantage of these improvements, it will be necessary to operate a lattice clock with a large number of atoms, and systematic frequency shifts resulting from atomic interactions will become increasingly important. We discuss how collisional frequency shifts can arise in an optical lattice clock employing fermionic atoms and describe a novel method by which such systematic effects can be suppressed.

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Many-Body Physics in an Optical Lattice Clock

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In this work we study the effect of interactions in an optical lattice clock based on fermionic Sr atoms. In current one-dimensional lattice clocks nuclear spin-polarized atoms are known to have contact interactions of p-wave character and collective in nature. Here we focus on interactions that will influence the design of future optical lattice clocks. We study the case where atoms are no longer confined to a single nuclear spin state. By using samples of atoms with different distributions among the ten nuclear spin states of Sr we show that these interactions are SU(N) symmetric up to a 3% uncertainty in our measurements. Through these measurements we are also able to determine all the s-wave and p-wave scattering lengths.\nWe also study the case of nuclear spin-polarized interacting atoms that are allowed to tunnel between different lattice sites where the electronic spin and the motion of these atoms become coupled. We observe spectroscopically the precession of the collective magnetization and evolution of spin locking effects arising from the interplay between p-wave interactions and interactions induced by the spin-orbit coupling. The many-body dynamics are captured by a spin model that describes a broad class of condensed matter systems ranging from superconductors to quantum magnets.\nBy loading a dense sample of atoms into a magneto-optical trap we are able to observe long-range dipole-dipole interactions between our Sr atoms. These interactions will be important for atomic clocks based on a three dimensional lattice, such as the one recently demonstrated in our lab. In these clocks it is possible to remove the contact interactions between the atoms by loading only one atom per lattice site. In this case the dominant interactions will be from the long-range dipole-dipole interactions that will take place between the atoms.

•Jan 1, 2018•0 citations

Ultra-high resolution spectroscopy with a87Sr optical lattice clock

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Recent results from the JILA 87Sr optical lattice clock are presented. Using the tight confinement of an optical lattice in combination wit a sub-Hz linewidth diode laser we have achieved a pulse-length limited linewidth of 1.8 Hz for the 1S0- 3P0 clock transition. This corresponds to a quality factor of Q ≈ 2.4 x 1014, and is a record for coherent spectroscopy. With the addition of a small magnetic bias field, the high line Q of the clock transition has also allowed us to resolve the nuclear-spin sublevels, and make a precision measurement of the differential Landé g-factor between the 1S0 and 3P0. We present the current accuracy and stability of the lattice clock, and in addition, we report on our development of precision tools for the lattice clock, including a stabilized clock laser, fs-comb based technology allowing accurate clock comparison in both the microwave and optical domains, and clock transfer over an optical fiber in an urban environment.

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We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at the 10-16fractional frequency level, currently limited by frequency shifts due to atomic interactions and room temperature blackbody radiation (BBR). We will discuss systematic measurements of collisional shifts and provide a complete theory to understand these interaction effects at the 10-17level. We will also discuss plans to interrogate atoms inside a cryogenic shield region to eliminate BBR shifts. We will present our recent successful efforts in improving the laser stability with the aim for the JILA Sr standard to reach the standard quantum measurement limit and achieve record levels of stability. Finally, a second Sr optical lattice clock has been constructed at JILA, and we will discuss the results of intercomparison experiments between the two standards.

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Abstract Precision measurement and frequency metrology have pushed many scientific and technological frontiers in the field of atomic, molecular and optical physics. In this article, we provide a brief review on the recent development of optical atomic clocks, with an emphasis placed on the important inter-dependence between measurement precision and systematic effects. After presenting a general discussion on the motivation and techniques behind the development of optical lattice clocks, where the use of many atoms greatly enhances the measurement precision, we present the JILA strontium optical lattice clock as the leading system of frequency metrology with the lowest total uncertainty, and we describe other related research activities. We discuss key ingredients that have enabled the optical lattice clocks with ultracold atoms to reach the 18th digit in both precision and accuracy. Furthermore, we discuss extending the power of precision clock spectroscopy to study quantum many-body physics and to provide control for atomic quantum materials. In addition, we explore future research directions that have the potential to achieve even greater precision.

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Probing many-body spin interactions with an optical lattice clock

Ana María Rey, Michael J. Martin, Matthew D. Swallows +6 more

Advances in ultra-stable lasers now permit sub-Hz resolution of optical atomic transitions. At this level, weak interactions by any ordinary scale can in fact dominate the dynamics of the interrogated atoms, even for spin polarized fermions at ultralow temperatures. Contrary to results obtained in radio frequency spectroscopy of alkali fermionic atoms, optical spectroscopy of 87 Sr and 171 Yb has revealed density dependent frequency shifts of the 1 S0 - 3 P 0 “clock” transition. Understanding interactions in these systems is necessary to improve their accuracy and stability. Moreover, such an understanding will enable optical lattice clock systems to serve as quantum simulators for open, driven, strongly-interacting quantum systems at the mesoscopic scale. In this talk we presented our progress towards a comprehensive evaluation and understanding of the interactions present during spectroscopy of the 87 Sr clock transition under various operating conditions. Our studies indicate that a mean-field solution of a master equation is sufficient to capture the many-body dynamics of alkaline earth atom clocks. Entering the regime in which a treatment beyond mean-field is required for a proper description of the clock dynamics is under immediate experimental reach.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•May 1, 2012•1 citation
Strontium optical lattice clocks at JILA recently demonstrated record-high accuracy and stability. These advances were enabled by an ultrastable laser with fractional frequency stability of 1x10-16 at 1 second. This laser allows us to study systematic shifts of the 1S0 to 3P0 clock transition with unprecedented precision. Density-dependent frequency shifts represent an unavoidable perturbation for clocks based on many atoms. Our studies of atomic interactions in an optical lattice clock system uncover the nature of these interactions and reveal important many-body atomic correlation effects in this open quantum system. By extending our measurements to all ten nuclear-spin sublevels of the clock states, we observe the first direct evidence of SU(N) symmetric interactions in alkaline earth(-like) atoms. Using the techniques we developed in these studies, we also demonstrate a novel technique for measuring the frequency noise spectrum of an ultrastable laser. We discuss designs for the future direction of our experiment which will place 87Sr atoms within a high finesse cavity that is resonant on the 1S0 to 3P1 transition. We will use this system to study collective effects in cavity quantum electrodynamics. Most notably, strong atom-cavity coupling can enhance the spectroscopic sensitivity of our clock by creating spin-squeezed states via quantum non-demolition measurements. As a precursor to future work studying cavity-mediated collective behavior, we use the unique atomic structure of 88Sr to investigate free-space retarded dipolar coupling in an optically thick sample of atoms.
We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at the 10-(16) fractional frequency level. An upgraded laser system has recently been constructed in our lab which may allow the JILA Sr standard to reach the standard quantum measurement limit and achieve record levels of stability. To take full advantage of these improvements, it will be necessary to operate a lattice clock with a large number of atoms, and systematic frequency shifts resulting from atomic interactions will become increasingly important. We discuss how collisional frequency shifts can arise in an optical lattice clock employing fermionic atoms and describe a novel method by which such systematic effects can be suppressed.
In this work we study the effect of interactions in an optical lattice clock based on fermionic Sr atoms. In current one-dimensional lattice clocks nuclear spin-polarized atoms are known to have contact interactions of p-wave character and collective in nature. Here we focus on interactions that will influence the design of future optical lattice clocks. We study the case where atoms are no longer confined to a single nuclear spin state. By using samples of atoms with different distributions among the ten nuclear spin states of Sr we show that these interactions are SU(N) symmetric up to a 3% uncertainty in our measurements. Through these measurements we are also able to determine all the s-wave and p-wave scattering lengths.\nWe also study the case of nuclear spin-polarized interacting atoms that are allowed to tunnel between different lattice sites where the electronic spin and the motion of these atoms become coupled. We observe spectroscopically the precession of the collective magnetization and evolution of spin locking effects arising from the interplay between p-wave interactions and interactions induced by the spin-orbit coupling. The many-body dynamics are captured by a spin model that describes a broad class of condensed matter systems ranging from superconductors to quantum magnets.\nBy loading a dense sample of atoms into a magneto-optical trap we are able to observe long-range dipole-dipole interactions between our Sr atoms. These interactions will be important for atomic clocks based on a three dimensional lattice, such as the one recently demonstrated in our lab. In these clocks it is possible to remove the contact interactions between the atoms by loading only one atom per lattice site. In this case the dominant interactions will be from the long-range dipole-dipole interactions that will take place between the atoms.
Recent results from the JILA 87Sr optical lattice clock are presented. Using the tight confinement of an optical lattice in combination wit a sub-Hz linewidth diode laser we have achieved a pulse-length limited linewidth of 1.8 Hz for the 1S0- 3P0 clock transition. This corresponds to a quality factor of Q ≈ 2.4 x 1014, and is a record for coherent spectroscopy. With the addition of a small magnetic bias field, the high line Q of the clock transition has also allowed us to resolve the nuclear-spin sublevels, and make a precision measurement of the differential Landé g-factor between the 1S0 and 3P0. We present the current accuracy and stability of the lattice clock, and in addition, we report on our development of precision tools for the lattice clock, including a stabilized clock laser, fs-comb based technology allowing accurate clock comparison in both the microwave and optical domains, and clock transfer over an optical fiber in an urban environment.
We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at the 10-16fractional frequency level, currently limited by frequency shifts due to atomic interactions and room temperature blackbody radiation (BBR). We will discuss systematic measurements of collisional shifts and provide a complete theory to understand these interaction effects at the 10-17level. We will also discuss plans to interrogate atoms inside a cryogenic shield region to eliminate BBR shifts. We will present our recent successful efforts in improving the laser stability with the aim for the JILA Sr standard to reach the standard quantum measurement limit and achieve record levels of stability. Finally, a second Sr optical lattice clock has been constructed at JILA, and we will discuss the results of intercomparison experiments between the two standards.
Abstract Precision measurement and frequency metrology have pushed many scientific and technological frontiers in the field of atomic, molecular and optical physics. In this article, we provide a brief review on the recent development of optical atomic clocks, with an emphasis placed on the important inter-dependence between measurement precision and systematic effects. After presenting a general discussion on the motivation and techniques behind the development of optical lattice clocks, where the use of many atoms greatly enhances the measurement precision, we present the JILA strontium optical lattice clock as the leading system of frequency metrology with the lowest total uncertainty, and we describe other related research activities. We discuss key ingredients that have enabled the optical lattice clocks with ultracold atoms to reach the 18th digit in both precision and accuracy. Furthermore, we discuss extending the power of precision clock spectroscopy to study quantum many-body physics and to provide control for atomic quantum materials. In addition, we explore future research directions that have the potential to achieve even greater precision.
Advances in ultra-stable lasers now permit sub-Hz resolution of optical atomic transitions. At this level, weak interactions by any ordinary scale can in fact dominate the dynamics of the interrogated atoms, even for spin polarized fermions at ultralow temperatures. Contrary to results obtained in radio frequency spectroscopy of alkali fermionic atoms, optical spectroscopy of 87 Sr and 171 Yb has revealed density dependent frequency shifts of the 1 S0 - 3 P 0 “clock” transition. Understanding interactions in these systems is necessary to improve their accuracy and stability. Moreover, such an understanding will enable optical lattice clock systems to serve as quantum simulators for open, driven, strongly-interacting quantum systems at the mesoscopic scale. In this talk we presented our progress towards a comprehensive evaluation and understanding of the interactions present during spectroscopy of the 87 Sr clock transition under various operating conditions. Our studies indicate that a mean-field solution of a master equation is sufficient to capture the many-body dynamics of alkaline earth atom clocks. Entering the regime in which a treatment beyond mean-field is required for a proper description of the clock dynamics is under immediate experimental reach.