11–20 of 152 posts
Earlier quoted context omitted.
Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…
ENIAC?
Earlier quoted context omitted.
Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…
ENIAC?
The state of each qbit is represented by a state vector of two complex numbers [a, b] where |a|^2 + |b|^2 = 1. There are two special qbit values called the classical basis: [1, 0] which is the classical bit 0, and [0, 1] which is the classical bit 1. If a qbit is not in one of the two classical states, we say it is in superposition. When a qbit is in superposition, we can measure it[0] and it will collapse probabilistically to 0 or 1; for a qbit [a, b], the probability that it collapses to 0 is |a|^2 and the probability that it collapses to 1 is |b|^2.
Things get more interesting when we have multiple qbits. If we have two qbits [a, b] and [c, d], we define their product state as their tensor product [ac, ad, bc, bd]. For example, if we have two qbits both in state [1/sqrt(2), 1/sqrt(2)], their product state would be [1/2, 1/2, 1/2, 1/2]. We use the product state to calculate the action of a quantum logic gate that operates on multiple qbits - for a gate which operates on two qbits, we can always represent its action as a 4x4 matrix.
Usually we can move back and forth between the product state representation and writing out the individual qbits states. However, in certain scenarios something very special happens: we cannot factor the product state back into the individual state representation! Consider the product state [1/sqrt(2), 0, 0, 1/sqrt(2)]. If you try to write this as a tensor product of two states [a, b] and [c, d], you cannot! It cannot be factored; the qbits have no individual value, and we say they are entangled.
Well, what does this mean? It means when you measure one qbit, even if the qbits are very far apart, you instantly know the value of the other qbit. So if I entangled two qbits in the state [1/sqrt(2), 0, 0, 1/sqrt(2)], give you one, then we go to opposite ends of the universe, if I measure my qbit and see a 0 I'll know your qbit instantly also collapsed to 0 (or collapsed to 1 if I measured 1). This phenomenon has been experimentally-verified to occur faster than light. It is instantaneous, as far as we can tell. So, local realism is wrong! Spooky action at a distance is real!
There is an important caveat: while the qbits seem to coordinate in some faster-than-light way, you cannot use this to communicate in a faster-than-light way. All we have is a shared random number generator. I can't send some chosen bit from my reference frame to yours. This is called the no-communication theorem.
If you found this interesting, I have a full video on quantum computing for computer scientists here: https://youtu.be/F_Riqjdh2oM
[0] IDGAF about your chosen quantum mechanics interpretation, don't @ me
Earlier quoted context omitted.
That's great. Now next thing that needs to be solved is to make this tech available for general public use just like computers are these days. Problems that are waiting to be solved by it are very large and of huge impact.
Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…
I visited USTC several years ago, (2014) and in this time they have basically doubled the number of qubits they can entangle, so this is a great step forward. At around ~100 qubits quantum computing becomes very useful, so maybe we won't have to wait too long.
That's great. Now next thing that needs to be solved is to make this tech available for general public use just like computers are these days. Problems that are waiting to be solved by it are very large and of huge impact.
Even software that is supposed to be useful is so terribly slow. Computers are between 2 and 4 orders of magnitude faster than programmers today experientially believe they are, because today’s culture of programming has rotted so thoroughly. Do you really need a quantum computer when 3 orders of magnitude are just sitting there on the table waiting to be picked up?
Earlier quoted context omitted.
That's great. Now next thing that needs to be solved is to make this tech available for general public use just like computers are these days. Problems that are waiting to be solved by it are very large and of huge impact.
Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…
Earlier quoted context omitted.
That's great. Now next thing that needs to be solved is to make this tech available for general public use just like computers are these days. Problems that are waiting to be solved by it are very large and of huge impact.
Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…
Many classical algorithms, which run in ~O(poly(n)) can have an 'equivalent' quantum algorithm in ~O(log(n)) - an exponential speedup. There is still debate as to how the complexity class of problems which are efficient on a quantum computer (BQP) relate to other complexity classes. Its suspected P lies entirely within BQP.
However, at least initially, I think quantum computers will be a specialized piece of equipment. Classical computing is pretty good for your average person. Quantum computers will be used for more heavy compute tasks.
I visited USTC several years ago, (2014) and in this time they have basically doubled the number of qubits they can entangle, so this is a great step forward. At around ~100 qubits quantum computing becomes very useful, so maybe we won't have to wait too long.
Even neater is that they are using quantum entanglement in radar to detect stealth planes: https://www.popsci.com/china-quantum-radar-detects-stealth-p...
From the article: they are planning to do this, and hopeful that it will work. Not actually using it yet.