How do you set a quantum bit? Is RSA dead?
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Agenda:
00:40 Lee talks about how to crack RSA and Shor's algorithm
The history of quantum computing. The 1st to propose it was Richard Feynman in the 1960s. Interest soon died out. 1990s - Dr. Shor published a paper saying if one could build a quantum computer with certain parameters, then one could factor a very large number
Today's security uses the RSA public key system and the Diffie Hellman Key Exchange algorithm
HTTPS uses the Diffie Hellmen Key Exchange algorithm. RSA stands for Rivest, Shamir, and Adelman
4:00 RSA works only for people known to each other, Diffie Hellman works for anyone
5:00 Factoring numbers that consist of large prime numbers is the basis for RSA. The processing needed to factor them is too large to be practical
6:45 Shor's algorithm is fast enough to crack RSA. If one could build a quantum computer with enough quantum bits then use a machine language cycle time that is us or ms, then one could factor thousand bit numbers
7:50 When will they be built? Some say 10 years, others 50
8:45 What does a quantum computer look like? An architectural description is easier to describe. A quantum computer similar to a classical computer, a quantum computer is a co-processor that will co-exist with current forms of digital electronics
9:15 Shor's algorithm has a lot of common commands - if statements and for loops. But, quantum gates are used in a quantum processor
10:00 Because a quantum gate operates in time instead of space, the term "gate" isn't accurate
10:30 What quantum computers exist today? Some exist with just a few quantum bits. People claim they've created quantum computers with 21 quantum bits. But, there can be a lot of errors and noise. For example, can a proper setup and hold time be maintained?
11:50 The Schrodinger's Cat analogy - In reality, if you've put a piece of physics into a superimposed quantum state, a disturbance of it (photon impact) will cause it to collapse into the wrong state or collapse too early
13:15 Quantum bits have to be thoroughly isolated. We use vacuums or extreme cold temperatures (well below 1 degree Kelvin!)
13:45 Research companies making claims about the number quantum bits are not using solid state quantum computers.
The isolation of a quantum computer isn't be perfect, so there's a short lifetime for the computation before the probability of errors get's too high.
14:35 Why do we use a superposition of states? Why does the timing matter? If it collapses at the wrong time it returns a wrong answer. Shor's algorithm makes it easy to check for the right answer. And, you get a remainder of 0 or your don't. If mod(x) = 0, you know the answer is correct. The computation only has to be reliable enough because you can check your answer
16:15 If the odds of getting the right answer is high enough, it's ok to get the wrong answer on occasion.
16:50 How do you write a quantum bit? It depends on the physical system. You can write a quantum bit by putting energy in the system, i.e. using a very small number photon pulse with a specific timing and phase
18:15 Keysight helps quantum computer researchers generate and measure pulses with high levels of precision
The pulses are carefully timed and correlated with sub-nanosecond precision
19:40 What is a quantum bit? There are two common kinds.
1 - Ions in a vacuum trapped by lasers. The ions are static because they are held in place by standing waves. The vacuum can be at room temperature and the ions are low temp because they can't move
2. Josephson junctions in tank circuits (resonant circuit, LC circuit, tuned circuit) makes oscillations at microwave frequencies. Under the right conditions, they can behave like an abstract two state quantum system. You simply have to designate zero and one to different states of the system.
Probabilities are the wrong description, it;s actually complex quantum amplitudes.
24:30 Stupid question section:
"If you had Schrodinger's cat in a box, would you look or not?"
Watch to find out Lee's answer!
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