Cats wanted dead and alive: quantum technologies | Professor Ben Murdin | TEDxSurreyUniversitySalon
## Speaker Context
- Speaker identity: Expert in quantum physics (implied by topic and talk content).
- Audience: General audience, with occasional technical deep dives (implied by attempts to gauge understanding).
- Setting, occasion of the talk: Presentation, possibly at a conference (indicated by thanking sponsors and referencing previous speakers).
- Framing the speaker establishes for themselves up front: The topic of quantum physics; suggests understanding it is difficult ("it was sort of a trap really if I asked you that question because somebody much smarter than I did once said if you think you understand quantum physics then you actually haven't understood it properly").
- Framing the speaker establishes for themselves up front: Find the topic "so fascinating" because it is "mindboggling."
## People
- Ruth: Singer and musician, friend of the speaker, recipient of a proposal for her to have a band where she plays everything at once by obeying the laws of Quantum physics.
- Philip: Research student at University College London, colleague who helped position a single impurity atom on a silicon chip.
## Organizations
- EPSRC: Sponsor of the speaker.
## Places
- Sodium Street lamps: Location where quantum physics determines the color of the light.
- University College London: Institution where Philip is a research student.
## Tools, Tech & Products
- Sodium Street lamps: Used to demonstrate quantum physics related to light color.
- Guitar string: Used as an analogy for wave physics, plucked to demonstrate fundamental and harmonic modes.
- Detector: A device used in an experiment to measure if atoms pass through it.
- MRI scan: Technology using hydrogen atoms in the body to demonstrate quantum superposition (spinning clockwise and anticlockwise).
- Silicon computer chips: Technology that uses transistors, with current state-of-the-art being around 17 nanometers.
- Transistors: Components in computer chips; current information storage is based on whether the transistor is on or off (zero or one).
- Quantum transistors: Hypothetical transistors where the information can be both on and off at the same time.
- Quantum computer registers: System using quantum transistors to store multiple pieces of information exponentially.
- Laser pulses: Tools used to "pluck" atoms to induce oscillations.
## Concepts & Definitions
- Quantum physics: The field of physics being discussed; characterized by properties found at the atomic scale.
- Two places at once: A property of small things like atoms and electrons.
- Superposition State: A state where an atom (or system) can exist in multiple states at once (e.g., both spinning clockwise and anti-clockwise).
- H Alpha line: The bright red color emitted by hydrogen, at 656 nanometers.
- Fundamental mode: The basic motion when a string is plucked in the middle.
- Harmonic chord: A combination of multiple notes played simultaneously on a string.
- Interference pattern: A phenomenon where two waves can cancel each other out or amplify each other.
- Quantum Interference: Demonstrated in individual atoms, showing clear oscillations.
- Entangle: The action atoms can perform in a quantum computer, relating to superposition and multiple locations.
## Numbers & Data
- One or two: Suggested number of people who understand quantum physics (question asked to the audience).
- 656 nanometers: Wavelength of the H Alpha line.
- 488 nanometers: Color wavelength the speaker's responsible color corresponds to.
- Three-dimensional: Description of the electron's orbit around the hydrogen atom.
- Quarter of the way along: Point on a guitar string where a specific pluck/harmonic can be generated.
- 3/4 of the way along: Point on a guitar string where a specific pluck/harmonic can be generated.
- Two to two (or two states at once): The minimum number of states an atom can be in simultaneously (related to superposition).
- 10 to the^ of 26 atoms: Estimated number of atoms inside a cat.
- 17 nanometers: Approximate current smallest size of transistors.
- 20 billionths of a meter: Equivalent measurement for 17 nanometers.
- Two: Minimum number of excitations/states needed for the conceptual thought experiment (e.g., excited state and relaxed state).
- Four: Number of pieces of information stored in just two coupled atoms (theoretically).
- Eight: Number of pieces of information stored in three transistors (theoretically).
- 100: The approximate number of quantum transistors needed to beat a modern mobile phone.
## Claims & Theses
- Quantum physics is all around us.
- The color of sodium Street lamps is determined by quantum physics.
- The red color emitted by hydrogen is due to stimulated emission by hot blue objects (Stars).
- Electrons orbiting the hydrogen atom perform a three-dimensional version of wave oscillations.
- When an atom jumps from one state to another, it emits light of a very specific color corresponding to the energy jump.
- Waves produce interference; two waves can cancel or amplify each other.
- Atoms can behave like waves, similar to how waves interfere.
- Atoms can be put into a situation where they are in two places at once.
- If you don't look at the situation (make a measurement), objects can be in two states at once.
- The cat ought to be both alive and dead if the experiment is set up and left unobserved.
- The MRI scan puts hydrogen atoms in a superposition state (spinning clockwise and anti-clockwise).
- There isn't any information technology that uses the superposition idea yet.
- Quantum transistors and quantum computer registers would be really powerful for Quantum information technology.
- Individual impurity atoms can be positioned on the surface of a silicon chip with atomic precision.
- Demonstrating interference in individual atoms is evidence of quantum interference.
- Quantum World atoms can be made to split into several versions of themselves (superposition) and spread over multiple locations (entanglement).
- Only 100 Quantum transistors are needed to beat a modern mobile phone.
- Understanding quantum physics in children is important for better overall understanding.
## Mechanisms & Processes
- Light color determination: Based on quantum physics effects observed in sodium street lamps.
- Hydrogen emission mechanism: Stimulated emission of light (H Alpha line) by hot stars.
- Wave Oscillation (String/Electron): Plucking a string or considering an orbiting electron results in specific modes of oscillation (e.g., fundamental mode, first harmonic).
- Light Emission from Atom: Occurs when an atom jumps from one energy state to another, emitting light corresponding to the energy difference.
- Wave Interference: Occurs when adding two waves that can result in cancellation or amplification.
- At-rest probability: The probability of an atom being in an excited state decays over time.
- Quantum measurement: The act of observing the system forces the state (e.g., the cat to be alive OR dead).
- MRI process: Magnetic field forces hydrogen atoms into a superposition state, causing them to emit detectable radio waves.
- Superposition State (Spin): Hydrogen atoms are put into a state where they are simultaneously spinning clockwise and anti-clockwise.
- Quantum Computation: Basis requires manipulating superposition and entanglement across multiple atoms to perform all possible computations at once.
## Timeline & Events
- Period: History of quantum physics concepts being discussed.
- Event: The speaker recalling a previous interaction where someone claimed to understand quantum physics.
- Period: Time elapsed between putting an atom in an excited state and its decay back to a relaxed state.
- Event: The speaker's experience taking children to science fairs (Big Bang Science Fair, Raw Society Summer Science Fair).
## Examples & Cases
- Sodium Street lamps: Demonstrate quantum physics governing light color.
- Hydrogen/Stars: Illustrates stimulated emission where blue light stimulates red light emission (H Alpha line).
- Guitar String Plucking: Fundamental mode (plucked in middle), first harmonic (plucked a quarter way), and harmonic chord (plucked a quarter way with finger touch).
- Quantum Superposition (Schrödinger's Cat): Conceptual thought experiment where the cat is simultaneously poisoned and not poisoned if unobserved.
- MRI Scan: Case showing hydrogen atoms in superposition state, detectable via radio waves in the body.
- Silicon Transistors: Concrete examples of technology advancement (50 nm $\rightarrow$ 17 nm).
- Positioned Impurity Atom: Micrograph demonstrating a single impurity atom placed with atomic precision on a silicon crystal surface.
- Quantum Interference Demonstration: Showing clear oscillations and a stable, measurable spectrum of oscillations from individual atoms.
## Trade-offs & Alternatives
- Quantum vs. Classical: Ordinary objects/particles vs. waves (waves can interfere, objects typically do not).
- Information Storage: Classical bits (transistor on/off, 1 bit) vs. Quantum bits (both on/off simultaneously, exponentially more capacity).
- Cat Observation: Unobserved state (alive AND dead) vs. Observed state (alive OR dead).
- Location/State: Atom being in one location/state vs. being able to be in multiple locations/states simultaneously.
## Counterarguments & Caveats
- Caveat: "If you think you understand quantum physics then you actually haven't understood it properly."
- Caveat: The quantum behavior is not encountered in everyday life.
- Caveat: The cat/Schrödinger experiment is conceptually absurd.
- Caveat: The cat experiment is practically impossible due to the number of atoms (10^26 atoms).
- Caveat: The transistor information storage is limited to zero or one (classical binary).
- Caveat: The quantum behavior (superposition, entanglement) is much harder to achieve than classical computation.
## Methodology
- Experimentation (Implied): The standard process of measuring physical phenomena (e.g., using a detector, performing MRI).
- Modeling/Analogies: Using guitar strings and the electron orbit to explain quantum wave behavior.
- Thought Experimentation: Using Schrödinger's cat to explore quantum rules.
- Engineering Feat: Positioning a single impurity atom on a crystal surface with atomic precision.
## References Cited
- Sching (Schrödinger): Postulated the thought experiment involving the cat to show the absurdity of quantum physics.
- Previous speaker at the Ted conference: Mentioned in relation to the concept of "being scooped."
## Conclusions & Recommendations
- Recommendation: People should be exposed to quantum physics ideas at an early age.
- Recommendation: The field is moving towards bigger things obeying quantum principles.
- Final Goal: To make a big computer register using quantum principles.
## Implications & Consequences
- If quantum principles are obeyed by large objects: The ability to store exponentially more information than classical methods (e.g., beating a mobile phone with 100 quantum transistors).
- If superposition is misunderstood: The implication is a misunderstanding of reality itself (e.g., the cat being both alive and dead).
- If quantum understanding is not taught early: The general understanding of quantum physics will suffer.
## Open Questions
- What the speaker's superpower would be (requires obeying quantum laws).
- If the reader/listener understands quantum physics (implied by the initial question).
## Verbatim Moments
- "if you think you understand quantum physics then you actually haven't understood it properly"
- "it's mindboggling"
- "you can be really really powerful and you could do really amazing things if you could obey the laws of Quant physics yourself"
- "the color that they emit is a bright red color astronomers call it the H Alpha line it's 656 nanometers"
- "if I played in slow motion we can um see that putting your finger on the 12 fret that's the one with the two spots that's exactly halfway along plays this fundamental mode"
- "the cat can then be both poisoned and not poisoned"
- "the cat ought to be both alive and dead if I put all this stuff into a box close the box"
- "the sum of those two probabilities will be 100%"
- "I can't get to the next slide yes so my my sponsor epsrc and my friends who generated these these results"