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No that’s not how it works, quantum mechanics cannot be simulated efficiently on a classical computer, the state space grows exponentially with the number of de

No that’s not how it works, quantum mechanics cannot be simulated efficiently on a classical computer, the state space grows exponentially with the number of degrees of freedom, every degree has relative phases to every other degree even when only looking at pure states, that’s why even the largest super computers cannot simulate more than 50 quantum degrees of freedom currently (see quantum supremacy).

jncfhnb 2y ago
I’m not claiming quantum mechanics can be efficiently simulated on a normal computer. I’m questioning whether arbitrary quantum mechanics systems can be effectively simulated by a quantum computer.
- adrian_b 2y ago
  I have not seen any description of a general-purpose programmable quantum computer, which could simulate an arbitrary quantum system, like a digital computer. All the examples given that I have seen were for making a hardwired simulator for a concrete quantum system, e.g. some chemical macromolecule of interest, to be used much in the same way as analog computers were used in the past for simulating systems governed by differential equations too complex to be simulated by the early digital computers in an acceptable time.
  - jncfhnb 2y ago
    Are hard coded quantum simulators even the same thing though? Like, if we’re saying that the goal of a quantum simulator is merely to run a high dimensional problem and exploit the nature of qubits to make it simpler to handle those imaginary vectors and what not… Does that actually follow the same framework as “traditional” “quantum computing”, e.g. struggles with error correction / problem formulation specifically designed to avoid unnecessary calculations? It feels like although a quantum simulator could viably work to simulate a specific system, it shouldn’t make it any easier to actually understand the system it is simulating and could maybe just indicate how complex by the amount of variation in simulation outcomes (which isn’t useless). Is that accurate? Excuse my terminology here
fooker 2y ago
Simulation usually involves randomized and sampling algorithms, not a full state space exploration. A good part of theoretical chemistry today relies on simulating quantum systems.

jncfhnb 2y ago

I’m not claiming quantum mechanics can be efficiently simulated on a normal computer. I’m questioning whether arbitrary quantum mechanics systems can be effectively simulated by a quantum computer.

adrian_b 2y ago
I have not seen any description of a general-purpose programmable quantum computer, which could simulate an arbitrary quantum system, like a digital computer. All the examples given that I have seen were for making a hardwired simulator for a concrete quantum system, e.g. some chemical macromolecule of interest, to be used much in the same way as analog computers were used in the past for simulating systems governed by differential equations too complex to be simulated by the early digital computers in an acceptable time.
- jncfhnb 2y ago
  Are hard coded quantum simulators even the same thing though? Like, if we’re saying that the goal of a quantum simulator is merely to run a high dimensional problem and exploit the nature of qubits to make it simpler to handle those imaginary vectors and what not… Does that actually follow the same framework as “traditional” “quantum computing”, e.g. struggles with error correction / problem formulation specifically designed to avoid unnecessary calculations? It feels like although a quantum simulator could viably work to simulate a specific system, it shouldn’t make it any easier to actually understand the system it is simulating and could maybe just indicate how complex by the amount of variation in simulation outcomes (which isn’t useless). Is that accurate? Excuse my terminology here

fooker 2y ago

Simulation usually involves randomized and sampling algorithms, not a full state space exploration. A good part of theoretical chemistry today relies on simulating quantum systems.