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MRI doesn't use quantum mechanics
Quantum sensors are impractical
(Fig.1) External magnetic field B splits energy levels of NV center with electron's orbital magnetic moment = μB
Quantum sensors often mean nitrogen vacancy (= NV ) centers in diamond, which is a defect in the carbon lattice consisting of a substitutional nitrogen atom accompanied by a vacancy site.
Two energy level splitting (= between ±1 ) of of this NV center is wider in stronger external magnetic field B interacting with the NV center's electrons' magnetic moment equal to Bohr magneton (= μB ) caused by the electron's orbit, Not by the electron spin that is unreal ( this-p.2, this or this-p.4-(1), this or this-p.2-2 ).
As a result, the applied microwave's frequency (= energy ) resonating with the energy difference between the NV center's 0 and ±1 states is shifted depending on the external magnetic field B (= Zeeman splitting ), which is why this NV center in diamond is said to be a quantum magnetic sensor or a magnetometer.
↑ By applying microwave pulses of many different frequencies and seeing which microwave frequency is absorbed into the NV centers in diamond, we can know the magnitude of external magnetic field felt by the NV centers in diamond ( this or this-p.1-right-magnetic field sensing~p.2, this or this-p.3 ).
Quantum mechanics is completely irrelevant to any technologies such as quantum sensors, MRI, atomic clocks, transistors .., all of which use experimentally observed atomic energies and phenomena that cannot be predicted by the useless quantum mechanics.
Because quantum mechanics cannot solve its Schrodinger equations nor predict any multi-electron atomic energies used in these (quantum) sensors, and the electron spin is unreal.
All these (quantum) sensors are based on energy levels measured by experiments, which are Not predicted by the useless quantum mechanics ( this or this-2nd-paragraph shows NV centers were accidentally discovered, Not by quantum mechanical prediction ).
This research (= this-p.4-left uses experimental parameters, No quantum mechanical prediction.
This-p.7-left-Methods use density functional theory, which is an empirical theory (= No quantum mechanical prediction ) due to its dependence on artificially-chosen pseudo-potential or exchange-correlation (= XC ) energy functionals ( this or this-p.3-p.7, this-p.23-lower ).
This-p.3-4th-paragraph says -- Useless quantum DFT
"we first demonstrate the inaccuracy of the numerical hyperfine parameters
obtained with the industry standard VASP code (= DFT choosing unreal pseudo-potentials )... we carry out large-scale calculations for the NV center in diamond using
different exchange-correlation functionals (= choosing different energy functionals means No quantum mechanical prediction )"
Contrary to a lot of overhyped fake news, quantum sensors such as NV centers in diamond are impractical (= used only for research purpose ) due to uncertain vacancy positions, unstable energy states (= knowing precise magnitude of external magnetic field is impossible due to being easily influenced by NV centers' condition, this-p.2-3rd-paragraph ), and its needing excessive instruments such as microwave generators and detectors ( this-p.1-left-2nd-paragraph ).
This or this-abstract says -- Impractical NV centers
"Quantum magnetometry.. of nitrogen vacancy centers in diamond nano or microcrystals is a promising technology for sensitive, integrated magnetic-field sensors. Currently, this technology is still cost-intensive and mainly found in research ( this or this-1st-paragraph )."
This-abstract (2025) says -- Useless quantum sensors
"Nitrogen-vacancy centers have demonstrated significant potential (= "potential" means still useless ) as quantum magnetometers for
nanoscale phenomena and sensitive field detection,... However, it is challenging to achieve solid-state magnetometers that can
simultaneously possess high spatial resolution and high field sensitivity"
This or this-lower-Challenges (2026) say -- Impractical biosensors
"Despite promising hypothetical advantages, integrating nanodiamond sensors into biological systems has presented several practical challenges"
This-p.16-right (2025) says No mass production of quantum sensors
still No mass production of NV centers in diamond.
(Fig.2) Unreal quantum mechanical model cannot explain spin.
The current unphysical quantum mechanical model tries to express materials such as NV centers in diamond as one-pseudo-electron DFT or quasiparticle with artificially-chosen exchange and pseudo-potential ( this p.8-1st-paragraph ), which cannot predict electron spin.
Even this current mainstream (one-pseudo-electron) DFT (= density functional theory ) cannot explain NV center's energy levels or spin, as this p.4-2nd-paragraph says
"As mentioned above, DFT calculations of the excited states of the NV− center in diamond
have given contradictory results"
↑ This one pseudo-electron DFT model just artificially chooses fake exchange-correlation potential functionals, pseudo-potential ( this-p.7-left-methods, this-p.5-left-last-paragraph ) and basis set wavefunctions, which cannot predict nor prove the existent of spin.
This-p.8-right-1st-paragraph says -- DFT cannot predict
"choice of the functional is crucial. ... EC was shifted to reproduce
the experimental band gap, i.e., scissor correction was applied (= empirical correction without quantum mechanical prediction, this-middle-Nonlocal exchange-correlation functional )."
(Fig.3) NV center in diamond is too unstable to be practical
This NV centers in diamond are too fragile, and easily broken, degraded (= become inactive called decoherence, this p.2-2nd-paragraph, this p.1-left, this abstract, this-1.introduction-3rd-paragraph
).
And due to its susceptibility to a lot of irrelevant noise, precise detection of small magnetic field by NV center is impossible ( this p.1-right-top, this 2.3 ).
This p.2-upper says -- Noise problem
"One of the current serious problems is noise, which reduces sensitivity of
NV center diamond sensors by broadening of the spectral linewidth and reduces
spectral resolution of the device"
This p.1-abstract says -- Unstable sensor
"However, the promise of NV centers is hindered by a severe degradation of
critical sensor properties, namely charge stability and spin coherence, near surfaces ( 10 nm deep)." ← NV center is still useless due to its instability.
This p.3-1st-paragraphs say -- Noisy quantum sensor
"While this makes the NV center a powerful sensor, it
puts strict requirements for the surroundings. In fact, any noise or instability (and especially
nearby paramagnetic defects) can strongly degrade its excellent as-fabricated properties."
This p.2-2nd-paragraph says -- Impractical NV sensor
"Despite the high magnetic sensitivity of NVs and their very small size, measuring nano-scale magnetic field
sources using NVs is still a challenge. Next to high magnetic sensitivity, proximity to the field source is essential
for such sensors."
"Therefore, a high quality shallow layer of NVs is desirable. When using conventional implantation or growth techniques, shallow NVs (< 5 nm from the surface) are mostly stable in the neutrally charged state (= unusable as sensors, this 1.introduction-3rd-paragraph ). Even when a shallow NV maintains its charge, it usually has very short relaxation time leading to low magnetic sensitivity ( this-p.1-left-last-paragraph )"
This p.7-right-4th-paragraph and p.11-3rd-paragraph says
"For NV centres within a few tens of nanometres of the diamond surface,
surface-related charge instabilities and noise further degrade NV properties"
"Although there are promising opportunities, many challenges remain, probably calling for collaborations between multiple academic domains and industry"
See also This-p.2-I.introduction-left, This p.2-right, this p.18-8, this introduction-3rd-paragraph.
And it is impossible to produce NV centers in precise positions (= which affect their sensitivity to external magnetic fields ) inside diamond (= which means uncertain NV center sensitivities make it impossible to precisely measure the absolute value of the target magnetic field ), which fact makes the NV-center impractical as magnetometer.
↑ Because the sensitivity of NV center to magnetic field changes depending on the uncertain positions of NV centers or distance from diamond's surface ( this 1.introduction says distribution of NV centers at diamond is random, this abstract ).
This p.6-right-1st-paragraph says -- Inaccurate sensors
"Since there is No precise control of the NV center density and their proximity to the surface, NDs (= nano-diamonds ) suffer from variability in their sensitivity. Factors such as local strain anisotropy and crystal impurities also lead to spin and optical properties variations. This inhomogeneity results in inconsistent measurements among different NDs."
This-middle Challenges and road ahead says
"Despite their remarkable potential, NV centers still face certain challenges: (= still useless )"
" Scalability: Building large-scale quantum computers using NV centers requires precise placement and control of individual centers, which presents a significant technical hurdle."
"Fabrication Challenges: Engineering diamonds with well-defined NV centers at specific locations remains a complex process."
The fact that NV center is still useless despite longtime researches shows the idea that this too unstable NV center may become quantum magnetic sensor or qubit is unrealistic and just baseless hype.
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