towards understanding by critical constructive inquiry
tisdag 27 december 2022
Is Quantum Computing Possible?
The possibility of quantum computing was suggested by the famous physicist Richard Feynman some 50 years ago to meet the need of excessive computing power supposed to required to simulate atomic quantum systems on a conventional digital computer. Today much effort is spent on seeking to build a quantum computer operating with qubits instead of the bits of a digital computer.
The basic idea is that a qubit can represent a superposition of two states (both 0 and 1) instead of the single state of either 0 or 1 of a bit. For a system with $N$ qubits/bits this increases the number of logical states from $N$ with bits to $2^N$ with qubits, thus from linear to exponential.
a superconducting transmon qubit, which is made from superconducting materials such as niobium and aluminum, patterned on a silicon substrate.
Such systems are not natural qubits, but are instead formed by isolating two energy levels out of many to form our approximate qubit.
For a superconducting qubit to behave as the abstract notion of the qubit, we must have the device at drastically low temperatures to minimize ambient noise or heat that could excite the superconducting qubit and increase the error probability.
Once a system has cooled to the target temperature, which takes several days, the qubit reaches equilibrium at the ground state 0.
Quantum computing boils down to transforming qubits from one state to another by logical gates. It is a tricky subject with standard measurement and randomness playing a central role. The Hadamard gate creates a superposition of 0 and 1 by starting in either the state 0 or 1, which followed by standard measurement gives 0 or 1 with a probability of 0.5. Altogether this looks like flipping a coin, but the creation of superposition of 0 and 1 prior to measurement is a unique qubit feature.
Let us compare with the discussion in the previous post on a radiating atom in superposition of a ground state 0 and an excited state 1 under certain exterior forcing with frequency matching the difference of excited and ground state energies. In this case it is the exterior forcing which creates a superposition of the ground state and matching excited state. By varying the frequency of the exterior forcing, the atomic spectrum can be determined, which can be seen as a form of deterministic spectrum measurement. In this setting the spectrum of the atom is observable, but not the underlying electronic structure.
A bit can be realised as an atom with value 0 in non-radiating ground state and value 1 in radiating superposition of ground state and excited state, both deterministically observable/measurable. A bit is in direct contact with exterior forcing determining its value to be 0 or 1.
As a qubit a radiating atom would allow superposition of ground and excited state and thereby offer a richer playground of states for processing by certain logical gates performed with zero exterior forcing. But measuring the result would amount to exterior forcing destroying superposition to randomely deliver either ground or excited state. The richer processing would thus come with randomness and a net gain would seem to be possible only for very special problems including randomness.
Summary so far: A bit is in direct contact with exterior forcing allowing deterministic processing and reading without destruction of the state. A qubit must be insulated from exterior forcing during processing, while reading destroys the state and delivers a random result.
Main question to answer: Is superposition possible without radiation/exterior forcing? If No, quantum computing may be impossible.
In an environment with a uniform energy density equal to the excited state of an atom capable of radiating in lower ambient energy density (ie: not a plasmized atom), that atom indeed cannot radiate. Remember that energy can only flow from a higher to a lower energy density region, so if the ambient is at the same energy density as that necessary to excite the atom, there is nowhere for the energy of the excited state of the atom to flow. It will remain in its excited state.
Once that exterior forcing is removed and ambient energy density falls, there exists an energy density gradient, and thus the atom can radiatively emit.
Remember that all action requires an impetus... and that impetus is usually in the form of a gradient of some sort. In the case of energy flow, that impetus is an energy density gradient.
"But what about the ground state? Even ground-state atoms emit Larmor radiation in the form of virtual photons (a point charge undergoing angular acceleration in relation to its electric field will emit radiation, either photons or virtual photons), and given that virtual photons mediate the magnetic interaction, that's the reason that every single element in the Periodic Table exhibits some form of magnetism!"
Yes, the bound electron's ground-state orbital radius is predicated upon the ground-state energy density of the quantum vacuum... specifically the anisotropy of the ground state quantum vacuum... it fluctuates, with the ground state bound electron orbital radius reflecting the mean of the magnitude of those fluctuations.
Think about it... bound electron orbital radius increases when energy is added (up to the point that ionization occurs)... and we now know that by artificially lowering quantum vacuum energy density, we can induce an artificial Lamb shift to below the bound electron's usual ground state orbital.
If we were able to (we're not currently able to) completely block quantum vacuum wavemodes, the bound electron would spiral-in to the nucleus, transmuting the element as the bound electron and nucleal proton become a neutron. That would continue until no bound electrons existed for the atom, with the atom spitting out excess neutrons, successively transmuting the element up the Periodic Table to hydrogen, then into a quark/gluon soup... and giving off an awful lot of energy in the process.
This would have to be done in a well-shielded Casimir cavity. What happens when that quark/gluon soup exits the cavity and quantum vacuum energy density increases? It would attempt to form matter again, pulling energy from the quantum vacuum to form mainly hydrogen (H being the most energetically favorable element to form), with a bit of helium and possibly lithium formed, as well... same as happened at the beginning of the universe.
We've been so focused on fission and fusion as a power source that we've overlooked this route.
Inlägg
In an environment with a uniform energy density equal to the excited state of an atom capable of radiating in lower ambient energy density (ie: not a plasmized atom), that atom indeed cannot radiate. Remember that energy can only flow from a higher to a lower energy density region, so if the ambient is at the same energy density as that necessary to excite the atom, there is nowhere for the energy of the excited state of the atom to flow. It will remain in its excited state.
SvaraRaderaOnce that exterior forcing is removed and ambient energy density falls, there exists an energy density gradient, and thus the atom can radiatively emit.
Remember that all action requires an impetus... and that impetus is usually in the form of a gradient of some sort. In the case of energy flow, that impetus is an energy density gradient.
"But what about the ground state? Even ground-state atoms emit Larmor radiation in the form of virtual photons (a point charge undergoing angular acceleration in relation to its electric field will emit radiation, either photons or virtual photons), and given that virtual photons mediate the magnetic interaction, that's the reason that every single element in the Periodic Table exhibits some form of magnetism!"
Yes, the bound electron's ground-state orbital radius is predicated upon the ground-state energy density of the quantum vacuum... specifically the anisotropy of the ground state quantum vacuum... it fluctuates, with the ground state bound electron orbital radius reflecting the mean of the magnitude of those fluctuations.
Think about it... bound electron orbital radius increases when energy is added (up to the point that ionization occurs)... and we now know that by artificially lowering quantum vacuum energy density, we can induce an artificial Lamb shift to below the bound electron's usual ground state orbital.
If we were able to (we're not currently able to) completely block quantum vacuum wavemodes, the bound electron would spiral-in to the nucleus, transmuting the element as the bound electron and nucleal proton become a neutron. That would continue until no bound electrons existed for the atom, with the atom spitting out excess neutrons, successively transmuting the element up the Periodic Table to hydrogen, then into a quark/gluon soup... and giving off an awful lot of energy in the process.
This would have to be done in a well-shielded Casimir cavity. What happens when that quark/gluon soup exits the cavity and quantum vacuum energy density increases? It would attempt to form matter again, pulling energy from the quantum vacuum to form mainly hydrogen (H being the most energetically favorable element to form), with a bit of helium and possibly lithium formed, as well... same as happened at the beginning of the universe.
We've been so focused on fission and fusion as a power source that we've overlooked this route.