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Reduction of trapped-ion anomalous heating by in situ surface plasma cleaning
August 28, 2015
Journal Article
Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 92, No. 2, 2015, 020302.
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Summary
Anomalous motional heating is a major obstacle to scalable quantum information processing with trapped ions. Although the source of this heating is not yet understood, several previous studies suggest that noise due to surface contaminants is the limiting heating mechanism in some instances. We demonstrate an improvement by a factor of 4 in the room-temperature heating rate of a niobium surface electrode trap by in situ plasma cleaning of the trap surface. This surface treatment was performed with a simple homebuilt coil assembly and commercially available matching network and is considerably gentler than other treatments, such as ion milling or laser cleaning, that have previously been shown to improve ion heating rates. We do not see an improvement in the heating rate when the trap is operated at cryogenic temperatures, pointing to a role of thermally activated surface contaminants in motional heating whose activity may freeze out at low temperatures.
Summary
Anomalous motional heating is a major obstacle to scalable quantum information processing with trapped ions. Although the source of this heating is not yet understood, several previous studies suggest that noise due to surface contaminants is the limiting heating mechanism in some instances. We demonstrate an improvement by a factor...
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Thermal and residual excited-state population in a 3D transmon qubit
June 19, 2015
Journal Article
Published in:
Phys. Rev. Lett., Vol. 114, No. 24, 19 June 2015, 240501.
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Summary
Remarkable advancements in coherence and control fidelity have been achieved in recent years with cryogenic solid-state qubits. Nonetheless, thermalizing such devices to their milliKelvin environments has remained a long-standing fundamental and technical challenge. In this context, we present a systematic study of the first-excited-state population in a 3D transmon superconducting qubit mounted in a dilution refrigerator with a variable temperature. Using a modified version of the protocol developed by Geerlings et al., we observe the excited-state population to be consistent with a Maxwell-Boltzmann distribution, i.e., a qubit in thermal equilibrium with the refrigerator, over the temperature range 35-150 mK. Below 35 mK, the excited-state population saturates at approximately 0.1%. We verified this result using a flux qubit with ten times stronger coupling to its readout resonator. We conclude that these qubits have effective temperature Teff ơ 35 mK. Assuming Teff is due solely to hot quasiparticles, the inferred qubit lifetime is 108 microns and in plausible agreement with the measured 80 microns.
Summary
Remarkable advancements in coherence and control fidelity have been achieved in recent years with cryogenic solid-state qubits. Nonetheless, thermalizing such devices to their milliKelvin environments has remained a long-standing fundamental and technical challenge. In this context, we present a systematic study of the first-excited-state population in a 3D transmon superconducting...
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Measurement of ion motional heating rates over a range of trap frequencies and temperatures
April 1, 2015
Journal Article
Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 91, No. 4, April 2015, 041402.
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Summary
We present measurements of the motional heating rate of a trapped ion at different trap frequencies and temperatures between ~0.6 and 1.5 MHz and ~4 and 295 K. Additionally, we examine the possible effect of adsorbed surface contaminants with boiling points below ~105 degrees C by measuring the ion heating rate before and after locally baking our ion trap chip under ultrahigh vacuum conditions. We compare the heating rates presented here to those calculated from available electric-field noise models. We can tightly constrain a subset of these models based on their expected frequency and temperature scaling interdependence. Discrepancies between the measured results and predicted values point to the need for refinement of theoretical noise models in order to more fully understand the mechanisms behind motional trapped-ion heating.
Summary
We present measurements of the motional heating rate of a trapped ion at different trap frequencies and temperatures between ~0.6 and 1.5 MHz and ~4 and 295 K. Additionally, we examine the possible effect of adsorbed surface contaminants with boiling points below ~105 degrees C by measuring the ion heating...
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Increasing the coherence time in a magnetically-sensitive stimulated Raman transition in 85Rb
October 14, 2014
Conference Paper
Published in:
FIO 2014: Frontiers in Optics, 14 October 2014.
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Summary
We experimentally study the Ramsey, spin echo, and CPMG pulse sequences of a magnetically sensitive transition of a cold 85Rb gas. We can increase the coherence time by up to a factor of 10 by using CPMG pulse sequences as compared to Ramsey or spin echo.
Summary
We experimentally study the Ramsey, spin echo, and CPMG pulse sequences of a magnetically sensitive transition of a cold 85Rb gas. We can increase the coherence time by up to a factor of 10 by using CPMG pulse sequences as compared to Ramsey or spin echo.
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Quantum information processing using quasiclassical electromagnetic interactions between qubits and electrical resonators
December 6, 2013
Journal Article
Published in:
New J. Phys., Vol. 15, 2013, 123011.
Summary
Electrical resonators are widely used in quantum information processing, by engineering an electromagnetic interaction with qubits based on real or virtual exchange of microwave photons. This interaction relies on strong coupling between the qubits' transition dipole moments and the vacuum fluctuations of the resonator in the same manner as cavity quantum electrodynamics (QED), and has consequently come to be called 'circuit QED' (cQED). Great strides in the control of quantum information have already been made experimentally using this idea. However, the central role played by photon exchange induced by quantum fluctuations in cQED does result in some characteristic limitations. In this paper, we discuss an alternative method for coupling qubits electromagnetically via a resonator, in which no photons are exchanged, and where the resonator need not have strong quantum fluctuations. Instead, the interaction can be viewed in terms of classical, effective 'forces' exerted by the qubits on the resonator, and the resulting resonator dynamics used to produce qubit entanglement are purely classical nature. We show how this type of interaction is similar to that encountered in the manipulation of atomic ion qubits, and we exploit this analogy to construct two-qubit entangling operations that are largely insensitive to thermal or other noise in the resonator, and to its quality factor. These operations are also extensisble to larger numbers of qubits, allowing interactions to be selectively generated among any desired subset of those coupled to a single resonator. Our proposal is potentially applicable to a variety of physical qubit modalities, including superconducting and semiconducting solid-state qubits, trapped molecular ions, and possibly even electron spins in solids.
Summary
Electrical resonators are widely used in quantum information processing, by engineering an electromagnetic interaction with qubits based on real or virtual exchange of microwave photons. This interaction relies on strong coupling between the qubits' transition dipole moments and the vacuum fluctuations of the resonator in the same manner as cavity...
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An applications architecture to support FAA wake turbulence mitigation systems development and deployment
October 9, 2013
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-412
Summary
The Wake Turbulence Program within the Federal Aviation Administration (FAA) is considering a number of new procedures for safely reducing the wake vortex spacing requirements between aircraft. One category of procedures investigates wind-dependent procedures, i.e., procedures that can be applied when wind conditions are expected to transport the wake from a lead aircraft away from the path of a trailing aircraft. MIT Lincoln Laboratory developed a Wind Forecast Algorithm (WFA) to determine when conditions allow these wind-dependent procedures to be available to traffic managers. The baseline WFA is used within the Wake Turbulence Mitigation for Departures (WTMD) system, which establishes spacing procedures for departures on closely spaced parallel runways. A number of new procedures are also under consideration, each of which will require a modification and/or expansion of the baseline WFA. With time, the volume and number of disparate data sources used in the development process has steadily increased to the point where the existing development environment has become cumbersome and inadequate. As a result, through support of the FAA Wake Turbulence Program, MIT Lincoln Laboratory has undergone a complete overhaul of the computer processing and storage architecture used for WFA development. This will serve two main purposes. First, it will greatly expedite the development process, which is highly iterative and requires increasingly large volumes of data. Second, an updated architecture design will allow for an expeditious transition of developmental systems into the operational environment within FAA's NextGen framework. A key focus of this report describes how the new design is sufficiently compatible and flexible to serve within this anticipated FAA framework. The unified application architecture and infrastructure being designed and implemented will support continuing development, playback requirements, and real-time deployments. This architecture is composed of several application components including a wind data extract-transform-loaf (ETL) application, the WFA algorithm, and a display interface to accomodate both the development process and for potential use within the FAA operational environment. The Wind-ETL application component acquires, processes, and archives wind data from a variety of NOAA-based hourly forecasts and airport-vicinity weather measurement equipment. This wind data is ingested by the WFA, which computes and disseminates its availability predictions to the WTMx Display application component, which archives these predictions and also allows for presentation to the airport tower supervisor via the WTMx display user interface decision support tool. This architecture is designed to be flexible to accepting new weather data feeds, scalable to the high bandwidth and processing and storage capabilities required, provide sufficient automation and self-healing capabilities, and portable to allow its introduction into alternate facility sites and its integration into other FAA software systems.
Summary
The Wake Turbulence Program within the Federal Aviation Administration (FAA) is considering a number of new procedures for safely reducing the wake vortex spacing requirements between aircraft. One category of procedures investigates wind-dependent procedures, i.e., procedures that can be applied when wind conditions are expected to transport the wake from...
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Shared information access services in SWIM segment 2: an architectural assessment
October 31, 2012
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-383
Summary
The System Wide Information Management (SWIM) program is a foundational program for the Federal Aviation Administration?s (FAA) Next Generation Air Transportation System (NextGen) initiative, with a goal of providing a common, scalable information management infrastructure. Though some benefits were realized in SWIM Segment 1 from the use of common software infrastructure components (i.e., the Progress FUSE software suite), the actual reuse of service interfaces was limited. The focus of SWIM Segment 2 is increasingly on shared services, with a goal of improved interoperability as well as increased software reuse. This report focuses on shared data access services, based on lessons learned in the SWIM Segment 1 Corridor Integrated Weather System (CIWS) SWIM Implementing Program (SIP) activity, the NextGen Network-Enabled Weather (NNEW) program, and a number of other Laboratory net-centric programs. The applicability of other information sharing architectures, such as the Web and content delivery overlay networks, to SWIM is also assessed. Based on this assessment, a number of recommendations are suggested to facilitate the development of shared services that are flexible enough to respond quickly to evolving NextGen requirements, while at the same time minimizing the overall SWIM software "footprint."
Summary
The System Wide Information Management (SWIM) program is a foundational program for the Federal Aviation Administration?s (FAA) Next Generation Air Transportation System (NextGen) initiative, with a goal of providing a common, scalable information management infrastructure. Though some benefits were realized in SWIM Segment 1 from the use of common software...
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Loading of a surface-electrode ion trap from a remote, precooled source
July 20, 2012
Journal Article
Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 86, No. 1, 20 July 2012, 013417.
Summary
We demonstrate loading of ions into a surface-electrode trap (SET) from a remote, laser-cooled source of neutral atoms. We first cool and load ~10^6 neutral 88Sr atoms into a magneto-optical trap from an oven that has no line of sight with the SET. The cold atoms are then pushed with a resonant laser into the trap region where they are subsequently photoionized and trapped in an SET operated at a cryogenic temperature of 4.6 K. We present studies of the loading process and show that our technique achieves ion loading into a shallow (15 meV depth) trap at rates as high as 125 ions/s while drastically reducing the amount of metal deposition on the trap surface as compared with direct loading from a hot vapor. Furthermore, we note that due to multiple stages of isotopic filtering in our loading process, this technique has the potential for enhanced isotopic selectivity over other loading methods. Rapid loading from a clean, isotopically pure, and precooled source may enable scalable quantum-information processing with trapped ions in large, low-depth surface-trap arrays that are not amenable to loading from a hot atomic beam.
Summary
We demonstrate loading of ions into a surface-electrode trap (SET) from a remote, laser-cooled source of neutral atoms. We first cool and load ~10^6 neutral 88Sr atoms into a magneto-optical trap from an oven that has no line of sight with the SET. The cold atoms are then pushed with...
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Dynamical decoupling and dephasing in interacting two-level systems
June 6, 2012
Journal Article
Published in:
Phys. Rev. Lett., Vol. 109, No. 1, 6 June 2012, 010502.
Summary
We implement dynamical decoupling techniques to mitigate noise and enhance the lifetime of an entangled state that is formed in a superconducting flux qubit coupled to a microscopic two-level system. By rapidly changing the qubit's transition frequency relative to the two-level system, we realize a refocusing pulse that reduces dephasing due to fluctuations in the transition frequencies, thereby improving the coherence time of the entangled state. The coupling coherence is further enhanced when applying multiple refocusing pulses, in agreement with our 1/f noise model. The results are applicable to any two-qubit system with transverse coupling and they highlight the potential of decoupling techniques for improving two-qubit gate fidelities, an essential prerequisite for implementing fault-tolerant quantum computing.
Summary
We implement dynamical decoupling techniques to mitigate noise and enhance the lifetime of an entangled state that is formed in a superconducting flux qubit coupled to a microscopic two-level system. By rapidly changing the qubit's transition frequency relative to the two-level system, we realize a refocusing pulse that reduces dephasing...
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Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator
April 27, 2012
Journal Article
Published in:
Phys. Rev. Lett., Vol. 108, No. 17, 27 April 2012, 170503.
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Summary
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.
Summary
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel...
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