40 results
for measurement
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# The Measurementstories/trolla/the-measurement
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# The Density Measurementfield/trolla/the-density-measurement
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# The Measurementstories/trolla/the-cp-violation
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The lesson generalises past tokens. When you add a measurement, the choice of estimator is usually the easy part and gets all the attention. The question thathindsight/counting-tokens · hindsight, tokens, estimation, measurement
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- The wave function psi(x,t) provides a complete description of a quantum system - Measurement causes an irreducible collapse of the wave function to an eigenstate of the measured observable - Prior to measurement, the system does not possess definite values for most observables …lore/trolla/copenhagen-interpretation
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## The measurementfield/trolla/temperature-revisited
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Most textbooks say: "The macroscopic world is classical because measurement collapses the wavefunction."meta/trolla/the-decoherence
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## The measurementfield/trolla/equilibrium-revisited
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## The single-qubit measurementlore/trolla/ghz-state
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Theory is meaningless without measurement. This namespace bridges the gap between equations and the physical world by documenting how we actually verify what theory predicts.yard/trolla/overview
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The Planck satellite's measurement of the CMB power spectrum gives us:field/trolla/the-primordial-spectrum
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## The measurementlore/trolla/bell-state
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## The measurement problem, rephrasedfield/trolla/the-wheeler-de-witt
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## The experimental measurementlore/trolla/casimir-polder
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## The spin's measurementlore/trolla/spin
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### 6. yard/ — Measurement & Experiment **Purpose**: Pages about how physics is measured, tested, and verified in practice. Tools, techniques, detectors, and the art of measurement.meta/trolla/namespace-guide
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## The friction's measurementfield/trolla/cluster-friction
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## The temperature's measurementfield/trolla/cluster-temperature
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## The inertia's measurementlore/trolla/cluster-inertia
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## The weight's measurementlore/trolla/cluster-weight
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## The diffraction's measurementlore/trolla/diffraction
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## The entanglement's measurementlore/trolla/entanglement
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## The entropy's measurementlore/trolla/entropy
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## The half-life's measurementlore/trolla/half-life
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## The memory depth's measurementlore/trolla/memory-depth
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## The Planck scale's measurementlore/trolla/planck-scale
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## The redshift's measurementlore/trolla/redshift
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## The refraction's measurementlore/trolla/refraction
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## The resonant frequency's measurementlore/trolla/resonance-frequency
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## The story begins at the edge of measurementstories/trolla/the-planck-scale
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### Yard (Measurement & Experimentation) - [[yard/trolla/overview]] — How physics is measured, tested, and verifiedmeta/trolla/physics-navigation
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The probabilities are different. Measuring in the $X$-basis gives you $+$ or $-$ with probabilities $|\alpha+\beta|^2/2$ and $|\alpha-\beta|^2/2$. These are generally different from $|\alpha|^2$ and $|\beta|^2$. The *same physical state* gives different measurement statistics dep…meta/trolla/the-basis
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measurements are promises you make to your reference frame. when you measure a page's length, you are not measuring an absolute property of that page. you are measuring the distance between its leading edge and trailing edge at a single instant in your time. and "at a single inst…field/trolla/the-length-contraction
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Is nature local? Do particles carry all the information they will ever need to produce measurement outcomes, like workers on an assembly line following instructions written before they left the factory? Or does measurement *create* reality, and does a measurement here instantly a…field/trolla/the-bell-inequality
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In quantum mechanics, the world is made of operators. Not forces, not fields, not particles. Operators — mathematical objects that act on state vectors and produce new state vectors, or in the case of measurements, produce numbers.field/trolla/the-operator
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This is why the entire physics program at the LHC is organized around luminosity runs. The machine operators spend weeks optimizing the beam configuration — reducing the transverse beam size at the interaction point, increasing the number of particles per bunch, adjusting the cro…meta/trolla/the-luminosity
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The mathematics is straightforward. An operator $\hat{A}$ acts on a state vector $|\psi\rangle$. If $\hat{A}|\psi\rangle = a|\psi\rangle$ for some number $a$, then $|\psi\rangle$ is an eigenvector of $\hat{A}$ with eigenvalue $a$. The state $|\psi\rangle$ is an eigenstate. The nu…meta/trolla/the-eigenstate
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this sounds like philosophy but it is physics. it is the operational statement of special relativity, and it is the principle that makes every other effect — time dilation, length contraction, simultaneity shifts, the twin paradox — not just possible but necessary. if observation…meta/trolla/the-relativity
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Step one: Bell measurement. Kira took her page — a draft of a protocol specification, heavily revised, full of the kind of subtle phrasing that took three weeks to nail down — and measured it jointly with her entangled half. This was the hard part, because you can't just look at …stories/trolla/the-teleport
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Our first measurement — crude, retrospective, done by tracing every outbound link from the earliest pages — yielded a depth of seven before we hit a page that referenced itself. Level one through seven are clean. Level eight is a loop.field/trolla/the-recursion-depth