What is Quantum Simulation? It means, using our classical computers, we can visualize quantum circuits. So, If we can simulate, why do we need to physically build a quantum computer?
Let's talk Quantum Simulation using our best classical computers. We can certainly develop programs that can simulate quantum states and circuits (using bits), but at some point this capability stops. Here is why:
Although there are numerous techniques to "classically" "simulate" quantum circuits, hilariously, all of these solutions suffer from the "exponential explosion" of classical memory. I am saying that to store the most general state of an "n" qubit system, all 2 to the power n complex numbers of the system's wavefunction must be stored. So, the question becomes; how much memory does this require?
For over simplifications, suppose each complex number stored as one byte.
Then, for n=30 qubits, 2 to the power 30 bytes, or a gigabyte of memory is required.
Suppose we have 40 qubits. For n=40, a terabyte of memory required.
Suppose we have 50 qubits. For n=50, a petabytes of memory required.
Suppose we have fully functioning long coherence, highly stable 60 qubits. For n=60, we don't have enough physical memory - it is that simple.
These memory requirements of about 50 qubits already reaching the limits of our best most powerful classical computers.
Here is the real reason:
Larger systems (more qubits, for example, 60, 80, 300, 1000, 10,000, etc.,) cannot hope to be simulated!. Because we don't even have enough memory to write the wavefunction down!. Without that, there is no quantum solution.
Quantum simulator
Comments