Top Tweets for #phy131
Today in #PHY131 #QuantumForEveryone: The uncertainty principle says there's a tradeoff in the precision of some quantities, like position and momentum. @LIGO "squeezes" the uncertainty of one quantity, at the expense of increasing another's, to detect gravitational waves better.
Today in #PHY131 #QuantumForEveryone: Quantum repeaters use entanglement swapping to establish long-range entanglement, and then quantum teleportation can be used. Quantum networks can enable distributed quantum computing and sensing. We also played Entanglion by @IBMResearch.
Today in #PHY131 #QuantumForEveryone: Entanglement can't be used to transmit information faster than light. Quantum error correction spreads information across many entangled qubits so no one qubit carries much information. Entanglement can be used to teleport a qubit's state.
Y'day in #PHY131 #QuantumForEveryone: No-cloning makes quantum money resist counterfeiting. Quantum computers solve some problems faster than classical; DiVincenco gave criteria for building them. Entanglement is a quantum correlation. Bell tests show no local hidden variables.
Today in #PHY131 #QuantumForEveryone: Students got to use real quantum computers by @IBMQuantum to generate random numbers. The Money or Tiger game is a variation of Deutsch's algorithm, and a quantum approach can solve it with certainty.
Today in #PHY131 #QuantumForEveryone: Quantum waves move in ways consistent with their probabilistic nature, called unitary evolution. For a qubit, it's a rotation on the Bloch sphere. We played Qubit Touchdown and a new game, Qubit Flip, I adapted from @dajmeyer's penny game.
Today in #PHY131 #QuantumForEveryone: A quantum bit, or qubit, can be 0, 1, or a superposition of both. It can be represented by a point on a Bloch sphere, measured with respect to opposite points on the sphere, and used to generate random numbers and establish a secret key.
Today in #PHY131 #QuantumForEveryone: Thaumatropes show superimposed images (video). Similarly, waves are superpositions of distinct waves, like guitar string waves and light waves / polarization. Quantum objects are waves with superpositions with probabilistic outcomes.
Today in #PHY131 #QuantumForEveryone: Review of Part 1 of the course, which consists of seven units focusing on established quantum technologies. An exam on this is next!
Today in #PHY131 #QuantumForEveryone: Quantum particles can have intrinsic angular momentum, called spin, and act like little bar magnets. This yields fine and hyperfine energy levels for atomic clocks and astronomy, and also yields magnetic sensors and MRI machines.
Today in #PHY131 #QuantumForEveryone: In atoms, electrons' waves takes shapes called orbitals, which are responsible for chemistry. A quantum particle can tunnel through a barrier, yielding in scanning tunneling microscopes, flash memory, and this year's Nobel Prize in Physics.
Today in #PHY131 #QuantumForEveryone: The double slit experiment with electrons shows that matter has a wave nature, too. Video from https://t.co/MECDPU5LHA. An electron microscope uses electrons, which have shorter wavelengths than light, to view small objects, even atoms!
Today in #PHY131 #QuantumForEveryone: Computers store information using bits and process them using logic gates. Logic gates are made from switches, and modern computers use transistors as the switches, such as NPN transistors, which students used hands-on.
Today in #PHY131 #QuantumForEveryone: Applications of p-n junctions. Solar panels, diodes (including rectifying AC to DC), light emitting diodes (LEDs), photodiodes (including counting items on a conveyor belt, and photoelectric smoke detectors), and digital cameras.
Today in #PHY131 #QuantumForEveryone: (1) Light can excite an electron in a semiconductor, making it mobile and decreasing resistance. This is a photoresistor (pictured), which detects light. (2) The conductivity of a semiconductor can be modified by doping, or adding impurities.
Today in #PHY131: We started Unit 4 on Quantization of Energy in Condensed Matter. We did a fluorescence experiment with different colors of light, and we learned about conductors, insulators, and semiconductors and their band structure.
Today in #PHY131 #QuantumForEveryone: Atomic clocks are used for timing and synchronization in the internet, computer security, stock market, oil and gas exploration, power grid, and for imaging black holes. Furthermore, atomic clocks make GPS possible.
Today in #PHY131 #QuantumForEveryone: The quantized energy levels of atoms can be used to create lasers (PhET simulation pictured) and atomic clocks, the latter of which are used to define the second and meter.
Today in #PHY131 #QuantumForEveryone: The quantized spectra of atoms has many applications, including neon signs, fireworks, and spectroscopy (identifying elements in the sun's atmosphere, rotation of the sun and expansion of the universe with Doppler shift).
Today in #PHY131 #QuantumForEveryone: We built spectroscopes and observed the spectra of various atoms. Bohr's model of the atom explains the spectra, where electrons orbit in quantized shells and jump up or down shells by absorbing or emitting photons.
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