Science behind Quantum Computing

Transcript

1. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Science behind Quantum Computing TCS Innovation Labs Cyber Physical Systems Lab July 26, 2013 Sibi Quantum Mechanics
2. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Outline 1 Introduction 2 Basics 3 Breakdown in Classical Physics Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality 4 Heisenberg’s Uncertainty Principle 5 Schrodinger’s Cat Sibi Quantum Mechanics
3. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat No one fully understands quantum mechanics. - Steven Weinberg Sibi Quantum Mechanics
4. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Definition Branch of physics which deals with physical phenomena at microscopic scales. Best understood by unlearning many classical physics concepts ( Similar to learning functional language from an imperative background.) Sibi Quantum Mechanics
5. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Quantum Mechanics asserts that a particle’s does not have a position and a velocity. Aim of Quantum Mechanics is to calculate the range of possible particle positions and the relative probability of these functions. Explanation of particle has a position of 100 (+ or -) 1: Classical Mechanics: Particle has a position in the range 99-101. Quantum Mechanics: Particle is simultaneously all over the range 99-101. (Thinking about wave which can spread out helps here.) Sibi Quantum Mechanics
6. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Outline 1 Introduction 2 Basics 3 Breakdown in Classical Physics Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality 4 Heisenberg’s Uncertainty Principle 5 Schrodinger’s Cat Sibi Quantum Mechanics
7. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality According to classical physics, an electron orbiting a nucleus should lose energy by emission of radiation. Because of energy loss, it should gradually spiral in towards the nucleus. But this does not happen. Sibi Quantum Mechanics
8. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Outline 1 Introduction 2 Basics 3 Breakdown in Classical Physics Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality 4 Heisenberg’s Uncertainty Principle 5 Schrodinger’s Cat Sibi Quantum Mechanics
9. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Also famously called as the Ultraviolet Catastrophe Prediction of late 19’th century classical physics. Prediction: An ideal black body at thermal equilibrium will emit radiation with infinite power. This too doesn’t happen. Sibi Quantum Mechanics
10. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Outline 1 Introduction 2 Basics 3 Breakdown in Classical Physics Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality 4 Heisenberg’s Uncertainty Principle 5 Schrodinger’s Cat Sibi Quantum Mechanics
11. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Sibi Quantum Mechanics
12. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Anomalous stability of atom and molecule Rayleigh Jeans Catastrophe Wave Particle Duality Classical Physics can deal with wave or particles. However various experiments show that waves sometimes act as if they were stream of particles, and stream of particles act as if they were waves. Einstein’s Photoelectric Effect showed light behaved as a particle. Young’s double slit experiment showed light behaves like a wave. Sibi Quantum Mechanics
13. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Both position and velocity of a particle cannot be measured accurately. This is because by taking a measurement we inadvertently disturb the system as well. Sibi Quantum Mechanics
14. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Thought Experiment Experiment involves an imaginary setup. A cat sealed inside a box with Geiger counter attached to it. Inside the Geiger counter is a small amount of radioactive substance. The box is set up so that when the radioactive substance decays, a device smashes a vial of toxic gas, killing the cat inside. After an hour, until the box is open, there is no way to determine whether the cat inside is alive or dead, thus allowing the cat to be both alive and dead. Sibi Quantum Mechanics
15. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Interpretation HUP show’s that it’s impossible to directly observe this decay because it involves particles so small that any equipment we have to monitor them would interfere with what they’re doing. What actually happens is the entire world splits into a superposition of worlds where cat is alive, and those where it is dead. Subatomic particles routinely exist in superposition of states and correct predictions of the outcomes of certain experiments can only be made by taking these effects into account. In Quantum mechanical world, it is possible for a atom in the combined state ’decayed-not decayed’ in which it is neither one nor the other but somewhere in between. Sibi Quantum Mechanics
16. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Superpositon Atomic particles can exist in two or more states at once. Example: Room with five chairs all exactly the same size. Classical theory: You sit in one of the chair. End of story. Quantum theory: Electron enters the room and sits down in all five of them at once! Sibi Quantum Mechanics
17. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Entanglement When two particles interact, the can become linked such that the alteration of one causes a mirrored response in the other, despite a separation by arbitrarily large distances. It is a sub case of quantum superposition: Two particles continue to form a system even after they have been separated and continue to share a quantum state until a measurement has been made. Measuring the state of one, causes the other to take different state. Sibi Quantum Mechanics
18. Introduction Basics Breakdown in Classical Physics Heisenberg’s Uncertainty Principle Schrodinger’s Cat Recent development 23 July, 2013 (2 days ago) it was presented in Moscow that the rules of quantum mechanics may extend to much larger objects than we thought. Earlier people have been able to build superposition states containing only a few photons, but now it has been demonstrated successfully with 160 million photons. Raises interesting question: Is there a border between micro and macro level where quantum rules apply ? Or does quantum mechanics applies on all scales ? Sibi Quantum Mechanics