Editing Zero-point energy (section)

== Purported applications ==

Physicists overwhelmingly reject any possibility that the zero-point energy field can be exploited to obtain useful energy ([[work (physics)|work]]) or uncompensated momentum; such efforts are seen as tantamount to [[perpetual motion machine]]s.{{citation needed|date=February 2024}}

Nevertheless, the allure of free energy has motivated such research, usually falling in the category of [[fringe science]]. As long ago as 1889 (before quantum theory or discovery of the zero point energy) [[Nikola Tesla]] proposed that useful energy could be obtained from free space, or what was assumed at that time to be an all-pervasive [[Aether (classical element)|aether]].<ref>{{cite journal |last1=Peterson |first1=I. |date=1997 |title=Peeking inside an electron's screen |url=https://www.sciencenews.org/archive/physics-5 |journal=Science News |volume=151 |page=89 |access-date=24 October 2016}}</ref> Others have since claimed to exploit zero-point or vacuum energy with a large amount of [[Pseudoscience|pseudoscientific]] literature causing ridicule around the subject.<ref name="army">{{cite web |author=Aiken |first=Amber M. |title=Zero-Point Energy: Can We Get Something From Nothing? |url=http://info.publicintelligence.net/USArmy-ZeroPointEnergy.pdf |publisher=[[U.S. Army]] [[National Ground Intelligence Center]] |quote=Forays into "free energy" inventions and perpetual-motion machines using ZPE are considered by the broader scientific community to be pseudoscience.}}</ref><ref name=saf>{{Scientific American Frontiers |8 |2}}</ref> Despite rejection by the scientific community, harnessing zero-point energy remains an interest of research, particularly in the US where it has attracted the attention of major aerospace/defence contractors and the [[DoD|U.S. Department of Defense]] as well as in China, Germany, Russia and Brazil.<ref name=army/>{{sfnp|Scott|2004}}

=== Casimir batteries and engines ===
A common assumption is that the [[Casimir effect|Casimir force]] is of little practical use; the argument is made that the only way to actually gain energy from the two plates is to allow them to come together (getting them apart again would then require more energy), and therefore it is a one-use-only tiny force in nature.<ref name=army/> In 1984 [[Robert L. Forward|Robert Forward]] published work showing how a "vacuum-fluctuation battery" could be constructed; the battery can be recharged by making the electrical forces slightly stronger than the Casimir force to reexpand the plates.<ref>{{cite journal|last1=Forward|first1=Robert L.|title=Extracting electrical energy from the vacuum by cohesion of charged foliated conductors|journal=Physical Review B|date=1985|volume=30|issue=4|page=1700|doi=10.1103/PhysRevB.30.1700|bibcode=1984PhRvB..30.1700F}}</ref>

In 1999, Pinto, a former scientist at [[NASA]]'s [[Jet Propulsion Laboratory|Jet Propulsion Laboratory at Caltech]] in Pasadena, published in ''[[Physical Review]]'' his [[thought experiment]] (Gedankenexperiment) for a "Casimir engine". The paper showed that continuous positive net exchange of energy from the Casimir effect was possible, even stating in the abstract "In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved."{{sfnp|Pinto|1999}}

Garret Moddel at [[University of Colorado Boulder|University of Colorado]] has highlighted that he believes such devices hinge on the assumption that the Casimir force is a [[Conservative force|nonconservative force]], he argues that there is sufficient evidence (e.g. analysis by Scandurra (2001)<ref>{{cite arXiv|last1=Scandurra|first1=M.|title=Thermodynamic properties of the quantum vacuum|eprint=hep-th/0104127|year=2001}}</ref>) to say that the Casimir effect is a conservative force and therefore even though such an engine can exploit the Casimir force for useful work it cannot produce more output energy than has been input into the system.<ref>{{cite journal|last1=Moddel|first1=Garret|last2=Dmitriyevaa|first2=Olga|title=Extraction of Zero-Point Energy from the Vacuum: Assessment of Stochastic Electrodynamics-Based Approach as Compared to Other Methods|journal=Atoms|volume=7|issue=2|at=51|arxiv=0910.5893|year=2009|doi=10.3390/atoms7020051|s2cid=17095906|doi-access=free}}</ref>

In 2008, [[DARPA]] solicited research proposals in the area of Casimir Effect Enhancement (CEE). The goal of the program is to develop new methods to control and manipulate attractive and repulsive forces at surfaces based on engineering of the Casimir force.<ref>{{Cite web |date=2008 |title=Research in a Vacuum: DARPA Tries to Tap Elusive Casimir Effect for Breakthrough Technology |url=https://www.scientificamerican.com/article/darpa-casimir-effect-research/ |access-date=2024-02-22 |website=www.scientificamerican.com |publisher=Scientific American}}</ref>

A 2008 patent by Haisch and Moddel<ref>{{US patent|7379286}}.</ref> details a device that is able to extract power from zero-point fluctuations using a gas that circulates through a Casimir cavity. A published test of this concept by Moddel<ref>{{cite journal|last1=Dmitriyevaa|first1=Olga|last2=Moddel|first2=Garret|title=Test of zero-point energy emission from gases flowing through Casimir cavities|journal=Physics Procedia|date=2012|volume=38|pages=8–17|doi=10.1016/j.phpro.2012.08.007|url=http://ecee.colorado.edu/~moddel/QEL/Papers/DmitriyevaModdel12.pdf|bibcode=2012PhPro..38....8D|access-date=1 November 2016|archive-date=7 May 2021|archive-url=https://web.archive.org/web/20210507132503/https://ecee.colorado.edu/~moddel/QEL/Papers/DmitriyevaModdel12.pdf|url-status=dead}}</ref> was performed in 2012 and seemed to give excess energy that could not be attributed to another source. However it has not been conclusively shown to be from zero-point energy and the theory requires further investigation.<ref>{{cite thesis|type=Thesis for: MS|last1=Henriques|first1=Carlos|others=Advisors: Fernandes, Luis & Amaro, F.|title=Study of atomic energy shifts induced by Casimir cavities|date=2014|doi=10.13140/RG.2.1.4297.1608}}</ref>

=== Single heat baths ===
In 1951 [[Herbert Callen|Callen]] and Welton<ref name="ReferenceB"/> proved the quantum [[fluctuation-dissipation theorem]] (FDT) which was originally formulated in classical form by [[Harry Nyquist|Nyquist]] (1928)<ref name="ReferenceC"/> as an explanation for observed [[Johnson noise]]<ref name="ReferenceD"/> in electric circuits. Fluctuation-dissipation theorem showed that when something dissipates energy, in an effectively irreversible way, a connected heat bath must also fluctuate. The fluctuations and the dissipation go hand in hand; it is impossible to have one without the other. The implication of FDT being that the vacuum could be treated as a heat bath coupled to a dissipative force and as such energy could, in part, be extracted from the vacuum for potentially useful work.{{sfnp|Milonni|1994|p=54}} Such a theory has met with resistance: Macdonald (1962)<ref>{{cite journal |last1=MacDonald |first1=D. K. C. |date=1962 |title=On Brownian Movement and irreversibility |journal=Physica |volume=28 |issue=4 |pages=409–416 |bibcode=1962Phy....28..409M |doi=10.1016/0031-8914(62)90019-8}}</ref> and Harris (1971)<ref>{{cite journal|last1=Harris|first1=I. A.|title=Zero-point fluctuations and thermal-noise standards|journal=Electron. Lett.|date=1971|volume=7|issue=7|pages=148–149|doi=10.1049/el:19710095|bibcode=1971ElL.....7..148H}}</ref> claimed that extracting power from the zero-point energy to be impossible, so FDT could not be true. Grau and Kleen (1982)<ref>{{cite journal|last1=Grau|first1=G.|last2=Kleen|first2=W.|title=Comments on zero-point energy, quantum noise and spontaneous-emission noise|journal=Solid-State Electronics|date=1982|volume=25|issue=8|pages=749–751|doi=10.1016/0038-1101(82)90204-0|bibcode=1982SSEle..25..749G}}</ref> and Kleen (1986),<ref>{{Cite book|last1=Kleen|first1=W.|title=Noise in Physical Systems and 1/F Noise 1985|chapter=Thermal noise and zero-point-energy|date=1985|pages=331–332|doi=10.1016/B978-0-444-86992-0.50072-2|isbn=9780444869920|url=https://archive.org/details/noiseinphysicals00dami|url-access=limited}}</ref> argued that the Johnson noise of a resistor connected to an antenna must satisfy Planck's thermal radiation formula, thus the noise must be zero at zero temperature and FDT must be invalid. Kiss (1988)<ref>{{cite journal|last1=Kiss|first1=L. B.|title=To the problem of zero-point energy and thermal noise|journal=Solid State Communications|date=1988|volume=67|issue=7|pages=749–751|doi=10.1016/0038-1098(88)91020-4|bibcode=1988SSCom..67..749K}}</ref> pointed out that the existence of the zero-point term may indicate that there is a renormalization problem—i.e., a mathematical artifact—producing an unphysical term that is not actually present in measurements (in analogy with renormalization problems of ground states in quantum electrodynamics). Later, Abbott et al. (1996) arrived at a different but unclear conclusion that "zero-point energy is infinite thus it should be renormalized but not the 'zero-point fluctuations'".{{sfnp|Abbott et al.|1996}} Despite such criticism, FDT has been shown to be true experimentally under certain quantum, non-classical conditions. Zero-point fluctuations can, and do, contribute towards systems which dissipate energy.<ref name="cloudfront.escholarship.org"/> A paper by Armen Allahverdyan and Theo Nieuwenhuizen in 2000 showed the feasibility of extracting zero-point energy for useful work from a single bath, without contradicting the [[laws of thermodynamics]], by exploiting certain quantum mechanical properties.<ref name=Allahverdyan-2000/>

There have been a growing number of papers showing that in some instances the classical laws of thermodynamics, such as limits on the Carnot efficiency, can be violated by exploiting negative entropy of quantum fluctuations.{{sfnp|Scully et al.|2003}}{{sfnp|Scully|2001}}<ref>{{cite journal |last1=Galve |first1=Fernando |last2=Lutz |first2=Eric |title=Nonequilibrium thermodynamic analysis of squeezing |journal=Physical Review A |date=2009 |volume=79 |issue=5 |page=055804 |doi=10.1103/PhysRevA.79.055804 |bibcode=2009PhRvA..79e5804G}}</ref><ref>{{cite journal |last1=Dillenschneider |first1=R. |last2=Lutz |first2=E. |title=Energetics of quantum correlations |journal=EPL |date=2009 |volume=88 |issue=5 |page=50003 |doi=10.1209/0295-5075/88/50003 |bibcode=2009EL.....8850003D |arxiv=0803.4067|s2cid=119262651 }}</ref><ref>{{cite journal |last1=Huang |first1=X. L. |last2=Wang |first2=Tao |last3=Yi |first3=X. X. |title=Effects of reservoir squeezing on quantum systems and work extraction |journal=Physical Review E |date=2012 |volume=86 |issue=5 |page=051105 |doi=10.1103/PhysRevE.86.051105 |pmid=23214736 |bibcode=2012PhRvE..86e1105H|doi-access=free }}</ref><ref>{{cite journal|last1=Boukobza|first1=E.|last2=Ritsch|first2=H.|title=Breaking the Carnot limit without violating the second law: A thermodynamic analysis of off-resonant quantum light generation|journal=Physical Review A|date=2013|volume=87|issue=6|page=063845|doi= 10.1103/PhysRevA.87.063845|bibcode= 2013PhRvA..87f3845B}}</ref>{{sfnp|Roßnagel et al.|2014}}{{sfnp|Correa et al.|2014}}<ref>{{cite journal|last1=Abah|first1=Obinna|last2=Lutz|first2=Eric|title=Efficiency of heat engines coupled to nonequilibrium reservoirs|journal=EPL|year=2014|volume=106|issue=2|page=20001|doi= 10.1209/0295-5075/106/20001|arxiv= 1303.6558|bibcode= 2014EL....10620001A|s2cid=118468331}}</ref><ref>{{cite journal|last1=Gardas|first1=Bartłomiej|last2=Deffner|first2=Sebastian|last3=Saxena|first3=Avadh|title=Non-hermitian quantum thermodynamics|journal=Scientific Reports|year=2016|volume=6|page=23408|doi= 10.1038/srep23408|pmid= 27003686|pmc= 4802220|arxiv= 1511.06256|bibcode= 2016NatSR...623408G}}</ref>

Despite efforts to reconcile quantum mechanics and thermodynamics over the years, their compatibility is still an open fundamental problem. The full extent that quantum properties can alter classical thermodynamic bounds is unknown<ref>{{cite book|last1=Gemmer |first1=Jochen|last2=Michel |first2=M.|last3=Mahler|first3=Günter|title=Quantum Thermodynamics: Emergence of Thermodynamic Behavior Within Composite Quantum Systems|date=2009|publisher=Springer|isbn=978-3-540-70510-9|doi=10.1007/978-3-540-70510-9|url=https://cds.cern.ch/record/1339164}}</ref>

=== Space travel and gravitational shielding ===
The use of zero-point energy for space travel is speculative and does not form part of the mainstream scientific consensus. A complete [[Theory of everything|quantum theory of gravitation]] (that would deal with the role of quantum phenomena like zero-point energy) does not yet exist. Speculative papers explaining a relationship between zero-point energy and gravitational shielding effects have been proposed,<ref name="Haisch et al. 1994"/><ref>{{cite journal|last1=Noever|first1=David|last2=Bremner|first2=Christopher|title=Large-scale Sakharov condition|journal=AIAA 35th Joint Propulsion Conference and Exhibit|date=1999|doi=10.2514/6.1999-2146}}</ref><ref>
{{cite journal
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}}</ref><ref>{{cite arXiv|last1=Podkletnov|first1=Evgeny|last2=Modanese|first2=Giovanni|title=Impulse Gravity Generator Based on Charged YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−y</sub> Superconductor with Composite Crystal Structure|date=2001|eprint=physics/0108005}}</ref> but the interaction (if any) is not yet fully understood. According to the [[general theory of relativity]], rotating matter can generate a new force of nature, known as the gravitomagnetic interaction, whose intensity is proportional to the rate of spin.<ref>{{cite magazine|last1=Matthews|first1=Robert|title=Antigravity machine weighed down by controversy|magazine=New Scientist|date=21 September 1996|url=https://www.newscientist.com/article/mg15120480-800-antigravity-machine-weighed-down-by-controversy/|access-date=26 October 2016}}</ref> In certain conditions the gravitomagnetic field can be repulsive. In neutron stars for example, it can produce a gravitational analogue of the [[Meissner effect]], but the force produced in such an example is theorized to be exceedingly weak.<ref>{{cite arXiv|last1=Lano|first1=R. P.|title=Gravitational Meissner Effect|date=1996|eprint=hep-th/9603077}}</ref>

In 1963 [[Robert L. Forward|Robert Forward]], a physicist and aerospace engineer at [[Hughes Research Laboratories]], published a paper showing how within the framework of general relativity "anti-gravitational" effects might be achieved.<ref>{{Cite journal|first=R. L.|last=Forward|date=1963|url= http://u2.lege.net/culture.zapto.org_82_20080124/Om%20nya%20energik%E4llor/Energy%20papers%20%20%20%20Mina%20dokument/antigravidity/guide%20to%20antigravity.pdf|title=Guidelines to Antigravity|journal=American Journal of Physics|volume=31|issue=3|pages=166–170|doi= 10.1119/1.1969340|bibcode= 1963AmJPh..31..166F}}</ref> Since all atoms have [[Spin (physics)|spin]], gravitational permeability may be able to differ from material to material. A strong [[toroid]]al gravitational field that acts against the force of gravity could be generated by materials that have [[Chaos theory|nonlinear properties]] that enhance time-varying gravitational fields. Such an effect would be analogous to the nonlinear electromagnetic permeability of iron, making it an effective core (i.e. the doughnut of iron) in a transformer, whose properties are dependent on magnetic permeability.<ref>{{cite journal|last1=Forward|first1=R. L.|title=General Relativity for the Experimentalist|journal=Proceedings of the IRE|date=1961|volume=49|issue=5|pages=892–904|doi= 10.1109/JRPROC.1961.287932|bibcode=1961PIRE...49..892F|s2cid=51650940}}</ref><ref>{{cite arXiv|last1=Swain|first1=John|title=Gravitatomagnetic Analogs of Electric Transformers|eprint=1006.5754|class=gr-qc|year=2010}}</ref><ref>{{cite web|title=Physicist Predicts Gravitational Analogue Of Electrical Transformers|url=https://www.technologyreview.com/s/419695/physicist-predicts-gravitational-analogue-of-electrical-transformers/|work=MIT Technology Review|access-date=28 October 2016|date=6 July 2010}}</ref> In 1966 [[Bryce DeWitt|Dewitt]]<ref>{{cite journal|last1=DeWitt|first1=Bryce S.|title=Superconductors and Gravitational Drag|journal=Physical Review Letters|date=1966|volume=16|issue=24|pages=1092–1093|doi= 10.1103/PhysRevLett.16.1092|bibcode=1966PhRvL..16.1092D}}</ref> was first to identify the significance of gravitational effects in superconductors. Dewitt demonstrated that a magnetic-type gravitational field must result in the presence of [[Magnetic flux quantum|fluxoid quantization]]. In 1983, Dewitt's work was substantially expanded by Ross.<ref>{{cite journal|last1=Ross|first1=D. K.|title=The London equations for superconductors in a gravitational field|journal=Journal of Physics A|date=1983|volume=16|issue=6|pages=1331–1335|doi=10.1088/0305-4470/16/6/026|bibcode=1983JPhA...16.1331R}}</ref>

From 1971 to 1974 Henry William Wallace, a scientist at [[GE Aerospace (1960s)|GE Aerospace]] was issued with three patents.<ref>{{US patent|3626606}}.</ref><ref>{{US patent|3626605}}.</ref><ref>{{US patent|3823570}}.</ref> Wallace used [[Bryce DeWitt|Dewitt's]] theory to develop an experimental apparatus for generating and detecting a secondary gravitational field, which he named the kinemassic field (now better known as the gravitomagnetic field). In his three patents, Wallace describes three different methods used for detection of the gravitomagnetic field – change in the motion of a body on a pivot, detection of a transverse voltage in a semiconductor crystal, and a change in the specific heat of a crystal material having spin-aligned nuclei. There are no publicly available independent tests verifying Wallace's devices. Such an effect if any would be small.<ref>{{cite journal|last1=Barker|first1=B. M.|last2=O'Connell|first2=R. F.|title=The gravitational interaction: Spin, rotation, and quantum effects-a review|journal=General Relativity and Gravitation|date=1979|volume=11|issue=2|pages=149–175|doi=10.1007/BF00756587|bibcode=1979GReGr..11..149B|s2cid=121728055}}</ref><ref>{{cite journal|last1=O'Connell|first1=R. F.|title=The gravitational field of the electron|journal=Physics Letters A|date=1970|volume=32|issue=6|pages=402–403|doi=10.1016/0375-9601(70)90022-8|bibcode=1970PhLA...32..402O}}</ref><ref>{{cite journal|last1=O'Connell|first1=R. F.|last2=Rasband|first2=S. N.|title=Lense-Thirring Type Gravitational Forces Between Disks and Cylinders|journal=Nature|date=1971|volume=232|issue=35|pages=193–195|doi=10.1038/physci232193a0|bibcode=1971NPhS..232..193O}}</ref><ref>{{cite journal|last1=Peres|first1=Asher|title=Test of equivalence principle for particles with spin|journal=Physical Review D|date=1978|volume=18|issue=8|pages=2739–2740|doi=10.1103/PhysRevD.18.2739|bibcode=1978PhRvD..18.2739P}}</ref><ref>{{cite journal|last1=Obukhov|first1=Yuri N.|title=Spin, gravity, and inertia|journal=Physical Review Letters|year=2001|volume=86|issue=2|pages=192–195|doi=10.1103/PhysRevLett.86.192|pmid=11177789|bibcode=2001PhRvL..86..192O|arxiv=gr-qc/0012102|s2cid=35509153}}</ref><ref>{{cite journal|last1=Ritter|first1=R. C.|last2=Winkler|first2=L. I.|last3=Gillies|first3=G. T.|title=Search for anomalous spin-dependent forces with a polarized-mass torsion pendulum|journal=Physical Review Letters|date=1993|volume=70|issue=6|pages=701–704|doi=10.1103/PhysRevLett.70.701|bibcode=1993PhRvL..70..701R|pmid=10054182}}</ref> Referring to Wallace's patents, a [[New Scientist]] article in 1980 stated "Although the Wallace patents were initially ignored as cranky, observers believe that his invention is now under serious but secret investigation by the military authorities in the USA. The military may now regret that the patents have already been granted and so are available for anyone to read."<ref>{{cite magazine|department=Patents Review|title=Antigravity Not So Crazy After All|magazine=New Scientist|date=14 February 1980|volume=85|issue=1194|page=485|url=https://books.google.com/books?id=2yIbfsnnnVgC}}</ref> A further reference to Wallace's patents occur in an electric propulsion study prepared for the [[Air Force Research Laboratory|Astronautics Laboratory]] at [[Edwards Air Force Base]] which states: "The patents are written in a very believable style which include part numbers, sources for some components, and diagrams of data. Attempts were made to contact Wallace using patent addresses and other sources but he was not located nor is there a trace of what became of his work. The concept can be somewhat justified on general relativistic grounds since rotating frames of time varying fields are expected to emit gravitational waves."<ref>
{{cite journal
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 |journal=Contract F04611-88-C-0014, Astronautics Laboratory (AFSC), Air Force Space Technology Center, Space Systems Division, Air Force Systems Command, Edwards AFB, CA
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}}</ref>

In 1986 the [[U.S. Air Force]]'s then Rocket Propulsion Laboratory (RPL) at [[Edwards Air Force Base]] solicited "Non Conventional Propulsion Concepts" under a small business research and innovation program. One of the six areas of interest was "Esoteric energy sources for propulsion, including the quantum dynamic energy of vacuum space..." In the same year [[BAE Systems]] launched "Project Greenglow" to provide a "focus for research into novel propulsion systems and the means to power them".{{sfnp|Scott|2004}}<ref>{{cite journal|last1=Allen|first1=J. E.|title=Aeronautics-1903; aerospace-2003; ? ? 2103|journal=Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering|date=2005|volume=219|issue=3|pages=235–260|doi=10.1243/095441005X30252|s2cid=110771631}}</ref>

In 1988 [[Kip Thorne]] et al.<ref>{{cite journal | first=Kip | last=Thorne |author2=Michael Morris|author3=Ulvi Yurtsever| journal=[[Physical Review Letters]] | volume = 61 | issue=13| pages=1446–1449 | doi= 10.1103/PhysRevLett.61.1446 | title= Wormholes, Time Machines, and the Weak Energy Condition | date=1988 | url=http://authors.library.caltech.edu/9262/1/MORprl88.pdf | bibcode=1988PhRvL..61.1446M | pmid=10038800}}</ref> published work showing how traversable [[Lorentzian wormhole|wormholes]] can exist in spacetime only if they are threaded by quantum fields generated by some form of [[exotic matter]] that has [[negative energy]]. In 1993 Scharnhorst and Barton<ref name="Scharnhorst 1993"/> showed that [[Scharnhorst effect|the speed of a photon will be increased]] if it travels between two Casimir plates, an example of negative energy. In the most general sense, the exotic matter needed to create wormholes would share the repulsive properties of the [[Inflation (cosmology)|inflationary energy]], dark energy or zero-point radiation of the vacuum.<ref>{{cite book|last1=Wheeler|first1=J Craig|title=Cosmic Catastrophes|url=https://archive.org/details/cosmiccatastroph0000whee|url-access=limited|date=2007|publisher=Cambridge University Press|location=New York|isbn=978-0521857147|page=[https://archive.org/details/cosmiccatastroph0000whee/page/228 228]|edition=2nd}}</ref>

In 1992 [[Evgeny Podkletnov]]<ref>{{cite journal|last1=Podkletnov|first1=E.|last2=Nieminen|first2=R.|title=A possibility of gravitational force shielding by bulk YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−x</sub> superconductor|journal=Physica C: Superconductivity|date=1992|volume=203|issue=3–4|pages=441–444|doi=10.1016/0921-4534(92)90055-H|bibcode=1992PhyC..203..441P}}</ref> published a heavily debated<ref>{{cite journal|last1=Rounds|first1=Frederic N.|title=Anomalous Weight Behavior in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub> Compounds at Low Temperature|journal=Proc. NASA Breakthrough Propulsion Phys. Workshop|date=1998|volume=279|pages=physics/9705043|arxiv=physics/9705043|bibcode=1997physics...5043R}}</ref>{{sfnp|Woods et al.|2001}}<ref>{{cite arXiv |eprint=gr-qc/0603033v1 |first=M. |last=Tajmar |author2=Plesescu, F. |title=Experimental Detection of the Gravitomagnetic London Moment |date=2006 |author3=Marhold, K. |author4=de Matos, C. J. |name-list-style=amp}}</ref><ref>{{cite journal|last1=Robertson|first1=Glen A.|title=On the Mechanism for a Gravity Effect using Type II Superconductors|journal=NASA Technical Reports Server|date=1999|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990046249.pdf|access-date=26 October 2016}}</ref> journal article claiming a specific type of rotating superconductor could shield gravitational force. Independently of this, from 1991 to 1993 [[Ning Li (physicist)|Ning Li]] and Douglas Torr published a number of articles<ref>{{cite journal|last1=Li|first1=N.|last2=Torr|first2=D. G.|title=Effects of a gravitomagnetic field on pure superconductors|journal=Physical Review D|date=1991|volume=43|issue=2|pages=457–459|doi=10.1103/PhysRevD.43.457|pmid=10013404|bibcode=1991PhRvD..43..457L}}</ref><ref>{{cite journal|last1=Li|first1=Ning|last2=Torr|first2=D. G.|title=Gravitational effects on the magnetic attenuation of superconductors|journal=Physical Review B|date=1992|volume=46|issue=9|pages=5489–5495|doi=10.1103/PhysRevB.46.5489|pmid=10004334|bibcode=1992PhRvB..46.5489L}}</ref><ref>{{cite journal|last1=Torr|first1=Douglas G.|last2=Li|first2=Ning|title=Gravitoelectric-electric coupling via superconductivity|journal=Foundations of Physics Letters|date=1993|volume=6|issue=4|pages=371–383|doi=10.1007/BF00665654|bibcode=1993FoPhL...6..371T|s2cid=122075917}}</ref> about gravitational effects in superconductors. One finding they derived is the source of [[Gravitomagnetic field|gravitomagnetic flux]] in a [[type II superconductor]] material is due to [[Spin (physics)|spin alignment]] of the lattice ions. Quoting from their third paper: "It is shown that the coherent alignment of lattice ion spins will generate a detectable gravitomagnetic field, and in the presence of a time-dependent applied magnetic vector potential field, a detectable gravitoelectric field." The claimed size of the generated force has been disputed by some{{sfnp|Kowitt|1994}}<ref>{{cite journal|last1=Harris|first1=Edward G.|title=Comments on "Gravitoelectric-Electric Coupling via Superconductivity" by Douglas G. Torr and Ning Li|journal=Foundations of Physics Letters|date=1999|volume=12|issue=2|pages=201–208|doi=10.1023/A:1021621425670|s2cid=115204136}}</ref> but defended by others.{{sfnp|Woods|2005}}<ref>{{cite journal|journal=AIP Conf. Proc.|volume=813|pages=1415–1420|doi=10.1063/1.2169327|last1=Tajmar|first1=Martin|last2=de Matos|first2=Clovis|title=Gravitomagnetic Fields in Rotating Superconductors to Solve Tate's Cooper Pair Mass Anomaly|year=2006|arxiv=gr-qc/0607086|bibcode=2006AIPC..813.1415T|s2cid=24997124|url= https://cds.cern.ch/record/973877/files/0607086.pdf}}</ref> In 1997 Li published a paper attempting to replicate Podkletnov's results and showed the effect was very small, if it existed at all.<ref>{{cite journal|first1=N.|last1=Li|first2=D.|last2=Noever|first3=T.|last3=Robertson|first4=R.|last4=Koczor|first5=W.|last5=Brantley|title=Static Test for a Gravitational Force Coupled to Type II YBCO Superconductors|journal=[[Physica C]]|volume=281|issue=2–3|date=August 1997|pages=260–267|bibcode= 1997PhyC..281..260L|doi= 10.1016/S0921-4534(97)01462-7}}</ref> Li is reported to have left the University of Alabama in 1999 to found the company ''AC Gravity LLC''.{{sfnp|Lucentini|2000}} AC Gravity was awarded a [[United States Department of Defense|U.S. Department of Defense]] grant for $448,970 in 2001 to continue anti-gravity research. The grant period ended in 2002 but no results from this research were made public.<ref>{{cite web|url=http://www.acq.osd.mil/dpap/Docs/FY01RPT.doc|title=Annual Report on Cooperative Agreements and Other Transactions Entered into During FY2001 Under 10 USC 2371|publisher=DOD|page=66|access-date=6 March 2014|archive-date=1 August 2021|archive-url=https://web.archive.org/web/20210801183915/https://www.acq.osd.mil/dpap/Docs/FY01RPT.doc|url-status=dead}}</ref>

In 2002 [[Phantom Works]], [[Boeing]]'s advanced research and development facility in [[Seattle]], approached [[Evgeny Podkletnov]] directly. Phantom Works was blocked by Russian technology transfer controls. At this time Lieutenant General George Muellner, the outgoing head of the Boeing Phantom Works, confirmed that attempts by Boeing to work with Podkletnov had been blocked by Russian government, also commenting that "The physical principles – and Podkletnov's device is not the only one – appear to be valid... There is basic science there. They're not breaking the laws of physics. The issue is whether the science can be engineered into something workable"{{sfnp|Cook|2002}}

Froning and Roach (2002)<ref>{{Cite conference|last1=Froning|first1=H.|last2=Roach|first2=R.|title=Preliminary Simulations of Vehicle Interactions with the Quantum Vacuum by Fluid Dynamic Approximations|book-title=AIAA 38th Joint Propulsion Conference & Exhibit|date=2002|pages=52236|doi=10.2514/6.2002-3925|isbn=978-1-62410-115-1}}</ref> put forward a paper that builds on the work of Puthoff, Haisch and Alcubierre. They used fluid dynamic simulations to model the interaction of a vehicle (like that proposed by Alcubierre) with the zero-point field. Vacuum field perturbations are simulated by fluid field perturbations and the aerodynamic resistance of viscous drag exerted on the interior of the vehicle is compared to the Lorentz force exerted by the zero-point field (a Casimir-like force is exerted on the exterior by unbalanced zero-point radiation pressures). They find that the optimized negative energy required for an Alcubierre drive is where it is a saucer-shaped vehicle with [[toroid]]al electromagnetic fields. The EM fields distort the vacuum field perturbations surrounding the craft sufficiently to affect the permeability and permittivity of space.

In 2009, Giorgio Fontana and Bernd Binder presented a new method to potentially extract the Zero-point energy of the electromagnetic field and nuclear forces in the form of [[gravitational wave]]s.<ref>{{Cite journal |last1=Fontana |first1=Giorgio |last2=Binder |first2=Bernd |date=2009-03-16 |title=Electromagnetic to Gravitational wave Conversion via Nuclear Holonomy |url=https://aip.scitation.org/doi/abs/10.1063/1.3115561 |journal=AIP Conference Proceedings |volume=1103 |issue=1 |pages=524–531 |doi=10.1063/1.3115561 |bibcode=2009AIPC.1103..524F |issn=0094-243X|url-access=subscription }}</ref> In the spheron model of the nucleus,<ref>{{Cite journal |last=Pauling |first=Linus |title=The Close-Packed-Spheron Model of Atomic Nuclei and ITS Relation to the Shell Model |date=October 1965 |journal=Proceedings of the National Academy of Sciences |language=en |volume=54 |issue=4 |pages=989–994 |doi=10.1073/pnas.54.4.989 |issn=0027-8424 |pmc=219778 |pmid=16578621 |bibcode=1965PNAS...54..989P |doi-access=free }}</ref> proposed by the two times Nobel laureate [[Linus Pauling]], [[Neutronium|dineutrons]] are among the components of this structure. Similarly to a [[dumbbell]] put in a [[Gravitational wave|suitable rotational state]], but with nuclear mass density, dineutrons are nearly ideal sources of gravitational waves at X-ray and gamma-ray frequencies. The dynamical interplay, mediated by nuclear forces, between the electrically neutral dineutrons and the electrically charged core nucleus is the fundamental mechanism by which nuclear vibrations can be converted to a rotational state of dineutrons with emission of gravitational waves. Gravity and gravitational waves are well described by General Relativity, that is not a quantum theory, this implies that there is no Zero-point energy for gravity in this theory, therefore dineutrons will emit gravitational waves like any other known source of gravitational waves. In Fontana and Binder paper, nuclear species with dynamical instabilites, related to the Zero-point energy of the electromagnetic field and nuclear forces, and possessing dineutrons, will emit gravitational waves. In experimental physics this approach is still unexplored.

In 2014 [[Lyndon B. Johnson Space Center|NASA]]'s [[Advanced Propulsion Physics Laboratory|Eagleworks]] Laboratories announced that they had successfully validated the use of a [[Quantum Vacuum Plasma Thruster]] which makes use of the Casimir effect for propulsion.{{sfnp|White, March, Williams et al.|2011}}<ref>{{cite web|last1=Maxey|first1=Kyle|title=Propulsion on an Interstellar Scale – the Quantum Vacuum Plasma Thruster|url=http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/5058/Propulsion-on-an-Interstellar-Scale-the-Quantum-Vacuum-Plasma-Thruster.aspx|website=engineering.com|access-date=24 October 2016|date=11 December 2012}}</ref><ref>{{cite magazine|last1=Hambling|first1=David|title=Nasa validates 'impossible' space drive|url=https://www.wired.co.uk/article/nasa-validates-impossible-space-drive|magazine=Wired UK|access-date=24 October 2016|date=31 July 2014}}</ref> In 2016 a scientific paper by the team of NASA scientists passed peer review for the first time.{{sfnp|White, March, Lawrence et al.|2016}} The paper suggests that the zero-point field acts as [[De Broglie–Bohm theory|pilot-wave]] and that the thrust may be due to particles pushing off the quantum vacuum. While peer review doesn't guarantee that a finding or observation is valid, it does indicate that independent scientists looked over the experimental setup, results, and interpretation and that they could not find any obvious errors in the methodology and that they found the results reasonable. In the paper, the authors identify and discuss nine potential sources of experimental errors, including rogue air currents, leaky electromagnetic radiation, and magnetic interactions. Not all of them could be completely ruled out, and further peer-reviewed experimentation is needed in order to rule these potential errors out.<ref>{{cite magazine|last1=Drake|first1=Nadia|author1-link=Nadia Drake|last2=Greshko|first2=Michael|title=NASA Team Claims 'Impossible' Space Engine Works—Get the Facts|url=http://news.nationalgeographic.com/2016/11/nasa-impossible-emdrive-physics-peer-review-space-science/|archive-url=https://web.archive.org/web/20161122020601/http://news.nationalgeographic.com/2016/11/nasa-impossible-emdrive-physics-peer-review-space-science/|url-status=dead|archive-date=22 November 2016|access-date=22 November 2016|magazine=National Geographic|date=21 November 2016}}</ref>