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Current status of CSL experiment
Ando lab. seminar 3.2. 2018
Kentaro Komori
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ContentsØ Simple introduction of CSL model
Ø Picking up main experiments which set the upper limit of CSL model
Ø New ideas for improving the upper limit with a thin tungsten wire
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ContentsØ Simple introduction of CSL model
Ø Picking up main experiments which set the upper limit of CSL model
Ø New ideas for improving the upper limit with a thin tungsten wire
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Interpretations on quantum mechanicsØ MANY!Ø Most popular one: Copenhagen interpretation
Ø Many worlds interpretation, etc…Ø There is an interpretation which was denied by experiments such as
De Broglie-Bohm theory (an example of hidden variable theory).
Measurement System
the set of probabilities one value
Bell inequalities violation
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Objective collapse modelØ Similar to Copenhagen interpretation, but firmly objective
Copenhagen Objective collapseü Including collapseü Non-committal about the
objective reality of the wave function
ü Regarding the wave function as real
ü Random collapse (spontaneous localization)
Ø Ghirardi-Rimini-Weber theory Contaneous Spontaneous Localization (today’s topic)
Ø Penrose interpretation: gravitational stress in GR spacetime
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Continuous Spontaneous LocalizationØ Improved GRW theoryØ Stochastic non-linear modification of standard quantum mechanics
Ø Characterized by two phenomenological constants, a collapse rate 𝜆and a length 𝑟#
Ø Can be tested experimentally!
typical size for collapse
ü Time scale of collapse is too long to observe.
ü Quantum mechanics holds.
ü Rapid localizationü Emergence of the classical
worldlargesmall
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ContentsØ Simple introduction of CSL model
Ø Picking up main experiments which set the upper limit of CSL model
Ø New ideas for improving the upper limit with a thin tungsten wire
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Current status of CSL model testØ Some experiments set the
upper limits of two parameters.
Ø Having “lower limit”, which is totally different from the other violation search
Ø Particle type: 𝜆 𝑟#$ < 𝛼⁄Ø Oscillator type: 𝜆𝑟#$ < 𝛼(𝑟# < 𝐿)
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Current status of CSL model test
surviving area
Ø Some experiments set the upper limits of two parameters.
Ø Having “lower limit”, which is totally different from the other violation search
Ø Particle type: 𝜆 𝑟#$ < 𝛼⁄Ø Oscillator type: 𝜆𝑟#$ < 𝛼(𝑟# < 𝐿)
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Current status of CSL model testØ Some experiments set the
upper limits of two parameters.
Ø Having “lower limit”, which is totally different from the other violation search
Ø Particle type: 𝜆 𝑟#$ < 𝛼⁄Ø Oscillator type: 𝜆𝑟#$ < 𝛼(𝑟# < 𝐿)
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Current status of CSL model testØ Latent image formation
in photography
Adler, J. of Phys. A, 40, 2935 (2007)
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Latent image formation in photographyØ Latent image formation process:
AgBr emulsion
Ag+
Ag-
Br2
Ag2
repeat
a cluster (track)
developable
Ø If latent image formation constitutes measurement and CSL model is true, the state vector reduction must come from parameters:
𝜆 = 5×1012±$Hz(𝑟# = 1016𝑚)
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Current status of CSL model testØ Cold atoms
Bilardello+, Physica A, 462, 764 (2016)
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Cold atomsØ Observing position deviation of cold
atoms after laser cooling
Ø The deviation could be larger due to CSL compared with following usual QM
𝜆 𝑟#$⁄ < 5×108Hz𝑚1$
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Current status of CSL model testØ X ray emission (very
high frequency)Curceanu+, J. Adv. Phys. 4, 263 (2015)
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X ray emissionØ Observing X ray emission from
Germanium
Ø Energy spectrum of X ray could be larger when the electron is coupled with collapse field.
Ø Probing the collapse field at very high frequency ~ 1e18 Hz, where CSL may be not effective. 𝜆 𝑟#$⁄ < 9×10$Hz𝑚1$
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Current status of CSL model testØ Some experiments set the
upper limits of two parameters.
Ø Having “lower limit”, which is totally different from the other violation search
Ø Particle type: 𝜆 𝑟#$ < 𝛼⁄Ø Oscillator type: 𝜆𝑟#$ < 𝛼(𝑟# < 𝐿)
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Oscillator typeØ Random momentum diffusion occurring due to CSL
Ø White force noise like viscous thermal noise
𝑑: width
𝜌: density
𝑇: temperature
γ = 𝑄 𝜔@⁄ : damping rate
𝑆#BC = 𝜆𝑟#$ 𝜌 𝑑⁄𝑆DE = 𝑇 𝑄 𝜔@⁄
ü Higher density, shorter width, lower temperature, higher Q value, lower resonant frequency is better.
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Current status of CSL model testØ Previous cantilever
Vinante+, PRL 116, 090402 (2016)
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Previous cantileverØ Temperature dependence of
displacement spectrum silicon: 0.1 um
neodymium magnet: 4.5 um
3.084 kHz
10 mKü 25 mK saturation: unknown heat leak to
the cantileverü CSL would appear as a positive intercept.
𝜆𝑟#$ < 2×101$$Hz𝑚$
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Current status of CSL model testØ Lisa Pathfinder
Carlesso+, PRD 94, 124036 (2016)Helou+, PRD 95, 084054 (2017)
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Lisa PathfinderØ Free-falling oscillator without suspension
thermal noiseØ Wide frequency range ü Gold test mass:
large densityü Wide width and
room temperature, but ultra-low damping
𝜆𝑟#$ < 2×101$$Hz𝑚$
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Current status of CSL model testØ Improved cantilever
Vinante+, PRL 119, 110401 (2017)
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Improved cantileverØ The same group as
previous cantilever
Ø Position measurement by superconducting quantum interference device (SQUID)
Ø Higher Q value: Q~1e7 at 20 mK
silicon: 450*57*2.5 um
neodymium magnet: 31 um
40 um
20 um
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Improved cantileverØ Absolutely expected thermal
noise limit
Ø Floor noise comes from SQUID additive noise.
Ø Fitting:
𝑆G = 𝐴 +𝐵𝑓LM + 𝐶(𝑓$ − 𝑓P$)$
(𝑓$ − 𝑓L$)$+(𝑓𝑓L/𝑄)$
force noise
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Improved cantilever
Ø Dependence of B on T/Q
Ø Agreement with a linear behavior over the whole range
Ø Positive intercept due to mysterious force noise
𝐵 = 𝐵L + 𝐵P𝑇/𝑄
non-zero intercept!
other force noise thermal noise
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Improved cantileverØ Possible noise sources
considered
Ø The shaded area would be excluded after identifying.
ü back actionü vibrationü magnetizationü thermo-mechanicsü systematic error of Q
not dominant
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Improved Lisa PathfinderØ Reduced force noise: 1/3
Ø CSL sensitivity: 9 times improved
Ø Most strict limit
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ContentsØ Simple introduction of CSL model
Ø Picking up main experiments which set the upper limit of CSL model
Ø New ideas for improving the upper limit with a thin tungsten wire
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Original idea 1Ø Larger density and thinner test mass: tungsten
thin film (𝜌 =19.25 g/cm^3)
Ø Rotation sensed by optical lever
𝑆#BC = 𝜆𝑟#$ 𝜌 𝑑⁄𝑆DE = 𝑇 𝜔@ 𝑄⁄
𝑇 = 4 K𝑄 = 2000
tungsten wire: 3 um, 5 cm
50*25*0.015 mm
𝜔@/2𝜋 = 2.7 mHz
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Original idea 1𝑆#BC = 𝜆𝑟#$ 𝜌 𝑑⁄𝑆DE = 𝑇 𝜔@ 𝑄⁄
Ø Demonstrated by Yoneta-kun
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Original idea 2Ø Making thin wire itself test massØ Shadow-sensing a violin mode of
thin wire (CuBe, tungsten)
𝑆#BC = 𝜆𝑟#$ 𝜌 𝑑⁄𝑆DE = 𝑇 𝜔@ 𝑄⁄
𝑇 = 1 K𝑄 = 10V
CuBe: 20 um 𝜔@/2𝜋 = 150 Hz
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Original idea 2𝑆#BC = 𝜆𝑟#$ 𝜌 𝑑⁄𝑆DE = 𝑇 𝜔@ 𝑄⁄
Ø Demonstrated by Oikawa-kun, Watanabe-kun
𝑄~108 !
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SummaryØ CSL is one of interpretation of quantum mechanics which can be
tested experimentally.
Ø Some experiments set good upper and lower limits resulting in a small surviving parameter space.
Ø Thin film as a torsion pendulum and thin wire as violin oscillating is an unique bed for improving the upper limit.
Ø Let’s do this ultra-hot CSL experiments!!!