File Name: atoms of space and time .zip
- What is relativity? Einstein's mind-bending theory explained
- Beyond space-time: Welcome to phase space
- NASA’s Cold Atom Lab (CAL): system development and ground test status
The possible use of loosely bound Rydberg atoms for remote gravimetric measurements is explored. A procedure to evaluate corrections of any order is outlined and applied to the 1 S state in a spherical symmetry. It is shown that observations of the effects described in this Letter near objects of neutron-star-like densities are possible in principle only in the absence of significant magnetic fields.
What is relativity? Einstein's mind-bending theory explained
Within this unique environment, atom traps can be decompressed to arbitrarily weak confining potentials, producing a new regime of picokelvin temperatures and ultra-low densities. Further, the complete removal of these confining potential allows the free fall evolution of ultracold clouds to be observed on unprecedented timescales compared to earthbound instruments.
This unique facility will enable novel ultracold atom research to be remotely performed by an international group of principle investigators with broad applications in fundamental physics and inertial sensing. The thermal, random motion of atomic gases fundamentally limits their free space measurement time and restricts their manipulation. Forty years of breakthroughs in the creation of ultracold quantum gases have resulted in standardized cooling techniques and technologies that are mature to the point of supporting large scale dedicated facilities, 1 , 2 , 3 portable field-ready devices, 4 , 5 , 6 and commercially offered components.
The first is access to a new parameter regime of quantum gases at picokelvin temperatures and ultra-low densities. Broadly, this is achieved by removing the asymmetric tilt that gravity introduces along one direction of the confining potential used to trap and cool atoms. It is then possible, for example, to decompress these traps far beyond what is achievable on the ground. Secondly, the wave nature of ultracold atoms released from these traps is the basis for inertial sensing atom interferometers, the precision of which scales as the square of their free space evolution time.
Recent milestones of these ruggedized, autonomous devices operating in reduced gravity include the generation of Bose—Einstein condensates BEC and the demonstration of matter-wave interferometry.
The persistent free fall condition of low Earth orbit is recognized as the next natural destination for cold atom work to take advantage of microgravity. Proposals include both satellite-based missions 21 , 25 , 26 , 27 , 28 and experiments to operate aboard the International Space Station ISS. Conceptually, the CAL system consists of three primary subsystems: the science module, electronics, and the laser and optical distribution system.
In order to support reliability, repair, integration, and replacement of components, all three subsystems leverage commercially offered components in an architecture intended to be compact, simple, and modular. This modular design has not only allowed parallel development of different subsystems but also various versions of the same subsystem. The electronics described in Materials and Methods reflect these ground versions. Instead, we evaporate only 87 Rb, which in turn sympathetically cools trapped potassium.
Our microwave evaporation protocol incorporates five linear frequency ramps that at low temperatures are interspersed with brief clearing stages at a second fixed frequency 6. For illustrative purposes, Fig. To the best of our knowledge, these results mark the first use of an atom chip to evaporate 87 Rb to condensation using microwaves, sympathetically cool either bosonic potassium isotope, and produce degenerate 41 K.
The 39 K atoms loaded onto the chip are initially so diffuse that our imaging fails to detect them. The last stage shows 70, 39 K atoms at a temperature of 1. However, at higher temperatures, we find it is possible to evaporate sufficiently with only a single frequency.
Following this simplified model, a harmonic magnetic trap with a higher trap bottom would therefore have a relatively larger region where two frequencies are necessary for efficient microwave evaporation. Following the work presented here, one science module will remain at JPL facilities for PI-specific experiment development and further optimization of dual species quantum gas production, while the primary science module is integrated into the fight instrument for acceptance testing and final ground verification as an autonomous instrument before delivery to the launch site.
In the subsequent commissioning phase, the flight system performance will be tested and optimized for microgravity with the option of data downlinked to the GDS in real time. The proposed research will investigate applications of atom interferometry for future precision measurements in the areas of Earth observation and fundamental physics, 47 , 48 Feshbach resonances to control differential center-of-mass distributions of dual-species quantum gas mixtures, 49 , 50 bubble-shell geometries for Bose—Einstein condensates, 51 as well as few-body systems in new temperature and density regimes that are prerequisites for the next generation of Efimov experiments.
Forming the outer boundary of the science module is a dual layer magnetic shield, which mitigates the significant and regularly modulated external magnetic fields experienced on the ISS.
Layered overview of the CAL science module. MOT coils are shown in red, with the central axis of coils oriented along the x-axis. Transfer coils in green are vertically offset from the MOT coils. Input for the optical pumping beam path orange arrow is positioned above the x -axis MOT beam collimator.
The collimators opposite the two cameras provide light for absorption imaging, while the collimator below the through-chip camera also provides the push beam.
The remaining two collimators surrounding the source cell send light to the 2D-MOT. Opposite the 2D- and 3D-MOT beam collimators are retro-reflecting mirrors the retro-reflecting mirror for the x -axis MOT beam is not visible from this orientation. These modifications include a second atomic source for potassium, specialized anti-reflective coatings, a unique configuration of atom chip conductive paths, as well as features for improved electrical, thermal, and mechanical integrity.
The source cell is surrounded by four rods lined with permanent magnets for the production of overlapped dual species 2D-MOTs. A smooth silicon chip with a 0. The CAL science cell is surrounded by ten rectangular-shaped magnetic coils, housed in an anodized aluminum structure that couples to the water cooling loop via eight thermal straps. These enclosed coils produce the fields necessary for the MOT, magnetic transport, transfer into a chip trap, and tuning near Feshbach resonances.
The coils are capable of generating magnetic bias fields along each Cartesian axis. Along the x -axis, independent coil control allows anti-Helmholtz configurations for magnetic trapping gradients. Two separate pairs of vertically offset x-coils translate the zero-field position from the MOT location to the atom chip.
Incorporated into these upper x-coils the transfer coils are two turns of wires designated as the fast Feshbach coils FFC. The upper side of the coil housing attaches to a breakout board for electrical connections to the atom chip, a microwave antenna, and a RF antenna. This breakout board also concentrically secures these loop-style antennas a few mm above the atom chip Fig.
Laser light is sourced from external cavity diode lasers ECDL , with a reference laser for each species, labeled a for K and d for Rb, locked to an atomic line via frequency modulated spectroscopy FMS. The potassium cooling b and repump c light is amplified in the same tapered amplifier TA , where we have observed no intensity fluctuations from potential mode competition.
The cooling and repump light for Rb and K is recombined and directed to both the 2D- and 3D-MOTs, while a switching assembly directs additional light to either the 2D-MOT push beam, the optical pumping path, or the imaging path.
This fiber path selection is determined by high-extinction fiber coupled LEONI mechanical switches on the sub-ms timescale, while short pulse generation is accomplished with Agiltron Nanospeed electro-optical switches. All switches are fiber coupled.
This full power is used for optical pumping, and attenuated to 0. A tunable microwave source results from mixing a separate AWG and voltage-controlled attenuator with the output of a synthesized CW generator.
We implement a fast and high-extinction ratio microwave switch followed by a chain of amplifiers. The capabilities of this ground test equipment allow us to set a fixed carrier wave at 6. The CAL flight electronics, however, produce one pure tone. We therefore adopted our procedure to follow the capabilities of the flight instrument.
Limitations to the trap lifetime result from noise on the current drivers sourcing the currents for the magnetic trap both the chip traces and coils and vacuum quality. We find that the lifetime is strongly influenced by the operation of the dispensers within the source cell, although any related change in vacuum quality is below the range of the ion pump gauge.
External to the physics package and coil housing is an aluminum structure that provides mechanical stability for collimators, mirrors, and two cameras relative to the physics package. Both cameras are thermally strapped to the water cooling loop.
Opposite the 2D- and 3D-MOT beam collimators are retro-reflecting mirrors, doubling the respective powers as seen by the atoms. As shown in Fig. The optical distribution system of CAL, on the ground and in flight, is based on commercially available lasers and components to create an all optical fiber-based distribution system Fig. We operate one laser system for both bosonic potassium isotopes at Laser cooling light is sourced by external cavity diode lasers New Focus Vortex Plus with a ruggedized design for flight.
The output light is guided through single-mode polarization maintaining fibers Corning PM and fiber splitter arrays from Evanescent Optics. One reference laser is stabilized to a temperature-controlled vapor cell module Vescent D via saturated absorption spectroscopy.
The other two lasers are stabilized via frequency offset locks to the D 2 cooling and repump transitions. Both TA outputs are distributed via fiber splitters and switches, providing light for 2D- and 3D- MOTs, absorption imaging, and optical pumping. All frequency adjustments are made by controlling the relative frequencies of the offset locks. While these TAs are capable of outputs up to 0. The drivers for both Leoni and Agiltron fiber switches are integrated within the switch assemblies.
RF and microwave sources are shown in Fig. Finally, experimental timing is accomplished with ColdQuanta's commercial computer control system.
Because complexity and size of the CAL instrument is reduced through the use of an all fibered distribution system, digital switches, a single tapered amplifier for each species, and overlapped MOTs, our potassium cooling strategy differs from other established techniques. We forego the sub-doppler cooling methods that require higher laser power and variable, independent intensity control of each K beam, 55 , 56 as well as the direct K evaporation methods that rely on an optical trap.
The prioritized laser cooling of 87 Rb closely follows the recipe described in Ref. Once the parameters for the simultaneous loading of Rb and K into the chip trap were found, returning to the most efficient loading of Rb alone required only minor adjustments to bias fields.
However, the absolute atom number and temperature is more favorable when loading Rb alone accomplished simply by shuttering the K light sources , owing mostly to the light induced collisions in the dual species MOT. We therefore summarize our loading of the chip trap assuming the presence of both Rb and K. Generally, we also find that very similar powers and detunings from the respective cooling and repump transitions work equally well for 41 K and 39 K.
We begin dual species MOT loading by initially applying rubidium light only. Both dispensers in the source cell are continuously operated at approximately 2. In order to limit the heating due to light assisted collisions, we unshutter the K light to load 41 K or 39 K on top of the rubidium during the last second of this loading phase. After the dual-species MOT loading, we shutter the push beams and compress each MOT by increasing the field gradient by a factor of 2.
Next, we effectively zero the magnetic field for 2. This optical pumping stage increases the number of trapped atoms by roughly a factor of 2.
The large overlap of the MOT coils and the transfer coils minimizes heating during this transport away from the MOT region.
In contrast, our chip trap is non-adiabatically loaded from the quadrupole of the transfer coils using a throw and catch method. The transfer currents are chosen to match the gradient that will be formed by the final chip trap as closely as possible, before we immediately switch the transfer currents from a gradient configuration to a bias in the x -direction as fast as the inductance of the coils allows.
This field is combined with bias fields in the y - and z -directions, and atom chip currents of 3. Kovachy, T. Quantum superposition at the half-metre scale. Nature , —
Beyond space-time: Welcome to phase space
By Amanda Gefter. Then along came Albert Einstein, who showed that different observers can disagree about the length of objects and the timing of events. His theory of relativity unified space and time into a single entity — space-time. It meant the way we thought about the fabric of reality would never be the same again. He and a trio of colleagues are aiming to take relativity to a whole new level, and they have space-time in their sights. If this radical claim is true, it could solve a troubling paradox about black holes that has stumped physicists for decades. So what is phase space?
Physicists have identified 13 building blocks that are the fundamental constituents of matter. Our everyday world is made of just three of these building blocks: the up quark, the down quark and the electron. This set of particles is all that's needed to make protons and neutrons and to form atoms and molecules. The electron neutrino, observed in the decay of other particles, completes the first set of four building blocks. For some reason nature has elected to replicate this first generation of quarks and leptons to produce a total of six quarks and six leptons, with increasing mass.
Atoms of Space-Time-Matter. • An STM atom is a fundamental description of an elementary particle, which produces and carries its own space-time geometry.
NASA’s Cold Atom Lab (CAL): system development and ground test status
Gravity and the Quantum pp Cite as. Equations of gravity when projected on space time horizons resemble Navier—Stokes equation of a fluid with a specific equation of state. Taking the view that the horizon fluid possesses some kind of physical reality beyond the formal mathematical similarity, we provide a statistical mechanical description for such fluids. We show that the model passes two crucial tests — obtaining the correct black hole entropy and negative bulk viscosity.
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Building on this base, over the last half of the 20th century physicists developed and tested a new quantum theory of matter now called the Standard Model and extended and tested the theory of classical space-time general relativity and big bang cosmology.