Category Archives: Quantum Theory

Q: What are “delayed choice experiments”? Can “wave function collapse” be used to send information?

Physicist: There are a lot of big claims made about entanglement, but there are two carved-in-stone facts that help cut through some of the more grandiose claims.  First, (maximally) entangled states always act exactly like a perfectly random state, until … Continue reading

Posted in -- By the Physicist, Entropy/Information, Experiments, Philosophical, Physics, Probability, Quantum Theory, Skepticism | 5 Comments

Q: Are there examples of quantum mechanics that can be seen in every-day life, or do they only show up in the lab?

Physicist: The weird effects that show up in quantum mechanics (a lot of them anyway) are due to the wave-nature of the world making itself more apparent.  What we normally think of as “particle behavior” is just what happens when … Continue reading

Posted in -- By the Physicist, Experiments, Quantum Theory | 17 Comments

Q: What does it mean for light to be stopped or stored?

Physicist: We’ve gotten a handful of questions since this was published and led to articles like this, this, and, this.  In a nutshell, some dudes in Germany (Georg Heinze, Christian Hubrich, and Thomas Halfmann) have found a method to shoot … Continue reading

Posted in -- By the Physicist, Computer Science, Entropy/Information, Experiments, Physics, Quantum Theory | 11 Comments

Q: What are quasi-particles? Why do phonons and photons have such similar names?

Physicist: Prefixes like “quasi-”, “psuedo-”, and sometimes “meta-” are basically used to mean “sorta like… but different… you know?”.  Quasiparticles behave like particles in a few fairly important ways, but aren’t actual particles at all.  The most important way, and … Continue reading

Posted in -- By the Physicist, Particle Physics, Physics, Quantum Theory | 4 Comments

Q: Why don’t “cheats” ever work on the uncertainty principle? What’s uncertain in the uncertainty principle?

Physicist: The Uncertainty Principle is often stated as “the position and momentum of a particle cannot be simultaneously and perfectly measured”.  Mathematically, it’s written as , which means that the product of the uncertainties in the position, x, and momentum, … Continue reading

Posted in -- By the Physicist, Physics, Probability, Quantum Theory | 3 Comments

Q: Do the past and future exist? If they do, is the future determined and what does that mean for quantum randomness?

Physicist: This is a difficult question to even ask, because the word “exist” carries with it some “time-based assumptions”.  For example, if you ask “does the Colossus of Rhodes exist?” the correct answer should be “it did, but it doesn’t … Continue reading

Posted in -- By the Physicist, Philosophical, Physics, Quantum Theory, Relativity | 36 Comments