Cats wanted dead and alive: quantum technologies | Professor Ben Murdin | TEDxSurreyUniversitySalon
The speaker argues that quantum physics, although mindboggling, is demonstrated in everyday phenomena like sodium street lamps and is not confined to abstract thought experiments. He illustrates this by explaining how atoms exhibit superposition and interference, culminating in the potential for quantum transistors that could revolutionize computing power. The necessity of early education in these concepts is emphasized to ensure broad understanding of this quantum reality.
## Speakers & Context
- Speaker: Expert in quantum physics (implied).
- Audience: General audience, with the speaker gauging understanding by asking for hands raised regarding knowledge of quantum physics.
- Setting: Presentation at a conference, acknowledging sponsors (EPSRC) and referencing previous speakers.
## Theses & Positions
- Quantum physics is pervasive in reality, influencing observable phenomena such as the color of sodium street lamps.
- The core concept of quantum mechanics is that small entities (atoms, electrons) can exhibit properties like being in multiple locations or performing multiple actions simultaneously.
- The speaker believes that if humans can master obeying quantum laws, they could achieve remarkable technological feats.
- Understanding quantum principles is crucial, and early exposure through science fairs is recommended to improve general comprehension.
## Concepts & Definitions
- **Quantum physics:** Field of physics governing behavior at the atomic scale.
- **Two places at once:** A property exemplified by atoms and electrons.
- **Superposition State:** State where an atom (or system) exists simultaneously in multiple states (e.g., both spinning clockwise and anti-clockwise).
- **H Alpha line:** Bright red color emitted by hydrogen, specifically at a wavelength of **656 nanometers**.
- **Fundamental mode:** The basic oscillation pattern observed when a string is plucked in the middle.
- **Harmonic chord:** Combination of multiple notes played simultaneously on a string, demonstrated by plucking at specific points.
- **Interference pattern:** Phenomenon where waves either cancel each other out or amplify each other.
- **Quantum Interference:** Evidence shown in individual atoms exhibiting clear, measurable oscillations.
- **Entangle:** Action atoms can perform, relating to superposition and multiple locations simultaneously.
## Mechanisms & Processes
- **Light Color Determination:** Quantum physics governs the color observed in sodium street lamps.
- **Hydrogen Emission Mechanism:** Emission of light occurs via stimulated emission when hot blue sources (Stars) stimulate the red emission line from hydrogen.
- **Wave Oscillation (String/Electron):** Plucking a string or considering an electron's orbit yields specific modes of oscillation (e.g., fundamental mode, first harmonic).
- **Light Emission from Atom:** Occurs when an atom transitions between energy states, emitting light corresponding to the energy gap.
- **Wave Interference:** Occurs when adding two waves, potentially resulting in amplification or cancellation.
- **At-rest probability decay:** The probability of an atom remaining in an excited state decays over time.
- **Quantum measurement:** The act of observation forces a system's state into a definite outcome (e.g., the cat being definitively alive OR dead).
- **MRI process:** Magnetic field forces body hydrogen atoms into a superposition state, causing them to emit detectable radio waves.
- **Quantum Computation:** Requires manipulating superposition and entanglement across multiple atoms to calculate all possible results simultaneously.
## Timeline & Sequence
- **Previous Interaction:** A moment where a previous speaker claimed to know quantum physics, leading the speaker to note, *"if you think you understand quantum physics then you actually haven't understood it properly."*
- **Energy Relaxation:** Time elapsed during the decay of an excited atomic state back to a relaxed state.
- **Educational Context:** Speaker recounts taking children to science fairs, including the Big Bang Science Fair and Raw Society Summer Science Fair.
## Named Entities
- **Ruth:** Singer and musician, friend of the speaker, proposed to be in a band playing all elements simultaneously while obeying quantum laws.
- **Philip:** Research student at University College London, colleague who managed to position a single impurity atom on a silicon chip.
- **Sodium Street lamps:** Location type whose light color is determined by quantum physics.
- **University College London:** Institution where Philip is a research student.
## Tools, Tech & Products
- **Sodium Street lamps:** Used to demonstrate quantum physics determining visible light color.
- **Guitar string:** Used as an analogy for wave physics, plucked to demonstrate fundamental and harmonic modes.
- **Detector:** Device used in an experiment to measure if atoms pass through it.
- **MRI scan:** Technology using hydrogen atoms in the body, which are forced into a superposition state, causing detectable radio wave emission.
- **Silicon computer chips:** Technology utilizing transistors; current state-of-the-art size is around **17 nanometers**.
- **Transistors:** Components whose information is stored by whether they are on or off (binary: zero or one).
- **Quantum transistors:** Hypothetical transistors capable of storing information as both on and off simultaneously.
- **Quantum computer registers:** System using quantum transistors to store multiple pieces of information exponentially.
- **Laser pulses:** Tools employed to stimulate atoms, inducing oscillations.
## Concepts & Definitions
- **Quantum physics:** Field of physics characterized by properties observed at the atomic scale.
- **Two places at once:** Property observed in small entities like atoms and electrons.
- **Superposition State:** State where an atom can exist in multiple states concurrently (e.g., spinning clockwise AND anti-clockwise).
- **H Alpha line:** Bright red color emitted by hydrogen, specifically **656 nanometers**.
- **Fundamental mode:** The basic oscillatory motion when a string is plucked in the center.
- **Harmonic chord:** Simultaneous playing of multiple notes on a string, achieved by specific plucking/touching.
- **Interference pattern:** Visual result when two waves interact, leading to constructive or destructive interference.
- **Quantum Interference:** Observable evidence of wave-like properties in individual atoms, showing clear oscillations.
- **Entangle:** The correlated behavior of atoms across multiple locations within a quantum computer.
## Numbers & Data
- Wavelength of H Alpha line: **656 nanometers**.
- Wavelength corresponding to the speaker's "responsible color": **488 nanometers**.
- Measurement for **17 nanometers**: Approximately **20 billionths of a meter**.
- Minimum states for superposition: **Two** (e.g., excited state and relaxed state).
- Information stored in two coupled atoms: **Four** pieces of information (theoretically).
- Information stored in three transistors: **Eight** pieces of information (theoretically).
- Approximate number of quantum transistors to match a modern mobile phone: **100**.
- Atoms required to calculate the number in a cat: **10^26**.
## Examples & Cases
- **Sodium Street lamps:** Demonstrate quantum physics dictating the color of the emitted light.
- **Hydrogen/Stars:** Illustrates stimulated emission where hot blue objects cause the emission of red light (**H Alpha line**).
- **Guitar String Plucking:** Demonstrates modes: fundamental mode (plucked center), first harmonic (plucked $\frac{1}{4}$ way), harmonic chord (combination).
- **Schrödinger's Cat:** Conceptual experiment illustrating the state where the cat is simultaneously poisoned AND not poisoned if unobserved.
- **MRI Scan:** Real-world example where hydrogen atoms are forced into a superposition state detectable by radio waves.
- **Silicon Transistors:** Concrete technology scale progression from **50 nm** to **17 nm**.
- **Positioned Impurity Atom:** Micrograph showing a single impurity atom positioned on a silicon crystal surface with atomic precision.
- **Quantum Interference Demonstration:** Measurement showing clear oscillations from individual atoms, confirming wave-like behavior.
## Tools, Tech & Products
- **Sodium Street lamps:** Used to demonstrate quantum physics in the real world.
- **Guitar string:** Used as a physical analogy for wave properties.
- **Detector:** Instrument used to confirm wave/particle interference patterns from atoms.
- **MRI scan:** Technology utilizing magnetic fields and hydrogen atoms to visualize body water content.
- **Silicon computer chips:** Modern information technology based on transistors.
- **Quantum transistors:** Hypothetical components capable of holding superposition states.
- **Quantum computer registers:** System architecture built from quantum transistors to perform parallel computation.
- **Laser pulses:** Tools used to manipulate atoms and induce measurable oscillations.
## References Cited
- **Sching (Schrödinger):** Person associated with formulating the thought experiment involving the cat.
- **Previous speaker at the Ted conference:** Mentioned in relation to the concept of *"being scooped."*
## Trade-offs & Alternatives
- **Information Storage:** Classical bits (limited to 0 or 1) versus quantum bits (potential for exponential information density).
- **Observation:** Unobserved quantum state (superposition) versus observed state (definite outcome).
- **Quantum Scaling:** Difficulty of scaling quantum effects to macroscopic objects compared to controlled atomic experiments.
## Counterarguments & Caveats
- **Misunderstanding:** The speaker warns that merely thinking one understands quantum physics does not constitute true comprehension.
- **Absurdity:** The cat experiment is acknowledged as being conceptually absurd.
- **Practical Limits:** The difficulty of performing the cat experiment due to the immense number of atoms ($\mathbf{10^{26}}$).
- **Technology Gap:** Currently, no information technology uses the superposition/entanglement principles in its functional design.
## Methodology
- **Modeling/Analogies:** Using plucked guitar strings and electron orbits to model quantum wave behavior.
- **Thought Experimentation:** Employing Schrödinger's cat to illustrate the measurement problem in quantum mechanics.
- **Micro-engineering:** Positioning a single impurity atom on a silicon crystal surface with demonstrated atomic precision.
- **Laser Manipulation:** Using laser pulses to induce and analyze atomic oscillations.
## Conclusions & Recommendations
- **Recommendation:** Early exposure to quantum concepts for children is highly beneficial for future scientific understanding.
- **Goal:** To build a quantum computer register capable of exponential computation by utilizing quantum transistors.
- **Future Vision:** The ultimate goal is mastering quantum laws for advanced technology, moving beyond the current binary limitations of computing.
## Implications & Consequences
- **Computing Power:** Just **100 Quantum transistors** are theoretically sufficient to surpass the computing capability of an ordinary mobile phone.
- **Understanding Reality:** Demonstrating that reality operates on a wave-particle duality governed by observation, rather than intuitive classical rules.
- **Technological Leap:** Quantum information technology promises a revolutionary change in computation capacity.
## Open Questions
- What the speaker's superpower would be, contingent on perfectly obeying quantum laws.
- If the audience members genuinely understand the fundamental principles of quantum physics.
## Verbatim Moments
- *"if you think you understand quantum physics then you actually haven't understood it properly"*
- *"it's mindboggling"*
- *"you could 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 only need 100 Quantum transistors in order to be able to beat that that phone"*
- *"it's a surreal idea"*
- *"I've actually had an experience of this going on... Big Bang Science Fair and the Raw Society Summer Science Fair"*