Solid-State Fusion (SSF) is a nuclear reaction (converting matter into energy) in the solid phase of matter, releasing heat that is in excess of input energy. Per Einstein's equation E = mc², when the nuclei of atoms break apart or come together there is a release of energy equal to the mass difference between the starting and ending products. Unlike conventional hot fusion, which powers our Sun, SSF does not require extreme temperatures or pressures. SSF also does not need radioactive elements likes uranium or plutonium that are used in conventional nuclear power plants. Many groups around the world have observed heat production from SSF when metallic materials are exposed to hydrogen isotopes at elevated temperatures.

• Solid-State Fusion (SSF) - SSF is an umbrella term that includes all types of nuclear reactions (fusion, fission, transmutation, beta decay, alpha decay) that occur in the solid-state. It is not limited to nuclear fusion and also includes condensed phases that are not completely solid.
• Cold Fusion - Following the announcement of Pons and Fleischmann in 1989, "Cold Fusion" was adopted by the popular media but following scrutiny and skepticism from the mainstream scientific community, "cold fusion" became associated with poor science. 4
• Low Energy Nuclear Reactions (LENR) - Following the DOE review of the field in 2003 5 LENR was increasingly adopted at the terminology for practitioners in the field. Scientifically, this term may be the most precise as it is not known whether the overall reaction is fission, fusion, etc, or a combination of them.
• Other terminologies - SSF has also been referred to as condensed matter nuclear science (CMNS), quantum hydrogen energy (QHE), lattice assisted nuclear reaction (LANR), and controlled electron capture reaction (CECR).

• Wendt and Irion (1922) - The phenomena of low-energy nuclear reactions (LENR) has been reported for decades from independent researchers from around the world. Perhaps better known by the term “cold fusion”, the observations suggest anomalous energy production on scale of nuclear reactions but produced from within chemical systems without extreme temperatures or pressures.6 
• Pons and Fleischmann (1989) - In March of 1989, electrochemists from the University of Utah, Drs. Martin Fleischmann and Stanley Pons, publicly announced a sustained nuclear fusion reaction at room temperature. 7  However, after unsuccessful attempts by multiple universities to replicate their results, they were met with intense criticism from established scientists. In hindsight, the dismissiveness was premature and private efforts in SSF development have persisted in the following decades.
• Google (2019) - Over a period of five years, a consortium of researchers led by Google conducted SSF experiments that resulted in a publication in Nature, one of the top journals in science. 8 Scientists from University of British Columbia (UBC), University of Maryland, MIT, and Lawrence Berkeley National Laboratory (LBNL) participated in this project. Although their paper did not show evidence of SSF, this effort legitimized SSF as a valid field of enquiry and has led to greater scientific and government interest.
• US Department of Energy (DOE) (2022) - For the first time, a US government agency has funded research in SSF.  The US DOE through their Advanced Research Projects Agency - Energy (ARPA-E) program issued a $10 million funding opportunity to support researchers from eight university group to conduct basic research on SSF. 9

• Nuclear Fission
  •  In late 1938, chemist/physicist Lise Meitner discovered something previously thought to be impossible: a uranium nucleus had split in two! When they shot lone neutrons into uranium atoms (element number 92), they found two lighter (lower atomic number) elements as a result. No one had imagined that one tiny neutron could cause a much larger nucleus to break apart. This process was thus dubbed fission.10 11
  • The energy released in a nuclear fission reaction is roughly 200 Mega electron-volts (MeV), explained by Einstein’s famous E = mc² equation, where mass, in this case a very small amount, can be transformed into quite a large amount of energy. It would take the equivalent of more than 13 barrels of oil to match the energy contained in just one gram of Uranium. 12
• Hot Nuclear Fusion 
  • At around the same time when scientists were trying to split the atom, another community of physicists looked into understanding the physics of the stars. In 1934 Ernest Rutherford observed enormous energetic effects when deuterium and helium nuclei were fused. It wasn’t until 1939 that Hans Bethe suggested a proton-to-proton fusion chain to explain the process by which the sun generates its energy. 13 
  • Light atomic nuclei fuse together under tremendous heat and pressure into heavier elements and release large amounts of energy in the process. Coulombic forces work to repel things carrying charges of the same sign, much like when two positive or negative ends of a magnet are brought together. The closer you push them the stronger the force driving them apart gets. Overcoming this resistance induces fusion through the strong nuclear force. 14 
• Solid-State Fusion (SSF)
  
  • Multiple groups around the world have reported observing excess heat in metal-hydrogen systems since 1989. Experiments generally use palladium metal electrodes with deuterated water, regular water, or mixed H-D in electrochemical and gas loading systems. Reports correlating excess measured heat with current density, loading, temperature, presence of helium, radio frequency (RF) emissions, neutron emissions, and gamma emissions have been made but are often difficult to recreate or build consensus regarding results explanation.
  • It is not clear at this time if the fundamental nuclear reactions comprising SSF is fission, fusion, beta decay, transmutation, or a combination of these.

• Have radiation or radioactive elements been detected during experiments? 
  • No, unsafe levels of neutrons or other radioactive products have not been detected 
  • No, unsafe levels of  gamma radiation has not been detected
• All current empirical evidence points to a safe and waste-free pathway to energy generation

• ICMNS
• Japan CFRS

The essential components in a SSF system are, for example, metallic materials and isotopes of hydrogen. The experimental setup can include these types of analysis.

• Heat detection (Calorimetry) - thermometer
• Transmutations - Induction coupled plasma mass spectroscopy (ICP-MS), neutron activation analysis (NAA)
  
• Radioactivity detection - neutrons, gamma rays, alpha and beta particles

• Detecting neutrons, elemental transmutation, and gamma or x-rays at very low concentrations
• Accurately measuring excess heat of the system
• Reproducibility of experiment and experimental set-up
• Quantum physics modeling that makes falsifiable predictions

No. Many models have been proposed on the mechanisms underlying SSF, however all of them are ad-hoc or self-limiting to specific observations only. Moreover, no hypothetical frameworks have been shown to predict the behavior of SSF systems when variables are changed.

Yes. While almost all technologies today have an established theoretical foundation, there are exceptions. The steam engine, which is arguably the most important energy technology, was developed and commercialized 30 years before the thermodynamics underlying the process was established. Similarly, it is possible that SSF can reach the market before we are able to understand the mechanism driving the SSF process.

From the transistors that power our smartphones to energy efficient lightbulbs to superconducting magnets, quantum technology plays an important role in our lives. In spite of the rapid advancement in technology, we are only scratching the surface in terms of understanding how matter works at the quantum or nanoscopic level (1 x 10^-9 m) or smaller. At these very small scales, our notions of traditional Newtonian physics do not apply. Quantum field theory suggests that electrons, neutrons, and protons, which make up our atoms, are in fact manifestation of excitations of entities known as fields. How these fields interact and how they can be controlled are still largely a mystery. It is believed that quantum interactions that are yet to be characterized lie at the heart of understanding and optimizing SSF.

Quantum science and engineering are multidisciplinary in nature. The following are examples of scientific and engineering disciplines that enable the study of SSF but are also benefited from SSF development.

• Quantum physics - Electron coherence, field enhancement, excitation
• Astrophysics and geophysics - Planetary, stellar, and cosmic elemental composition
• Chemistry and materials science - Field effects, nano-manufacturing, nano self-assembly, graphene, nanotubes
• Semiconductor engineering - Mass manufacturing of metal nanocatalysts 
• Electrical engineering  - Triggering devices, piezoelectronics, electronic circuitry, vacuum microelectronics
• Chemical engineering - Heat transfer systems, turbines
• Nuclear engineering - Radioactivity detection

• Julian Schwinger (Nobel Prize Winning Physicist, Quantum Electrodynamics)
• Brian Josephson (Nobel Prize Winning Physicist, Josephson junction in superconductivity)
• Hiroshi Komiyama (Former Dean of the University of Tokyo, Chemical Engineer, Chair of Mitsubishi Research)

The global energy industry, which is a $15 trillion market, powers our cities, industries, and our transportation. Over 80% of the energy today is obtained through fossil fuels. SSF, which can be scaled to from breadbox to a gigawatt power plant, could potentially replace all fossil fuels and be the ultimate safe, cheap, and clean energy source. 

A this stage, excess heat from SSF has been plausibly demonstrated by various groups around the world; however, it is not known whether these effects are commercializable. An SSF system that is either be self-powered or producing useful electrical energy has not been publicly shown. Furthermore, decisive evidence of a nuclear reaction remains elusive. 

No but a major boiler company in Japan has invested in SSF.

It is estimated that at least $15 million in government funding in EU, US, and Japan have been dedicated to SSF along with $150 million in private funding. 

• Power generation
• Cars and ships
• Boilers
• Chemical, petroleum, metals, and glass processing industries
• Direct Air Capture (DAC) for atmospheric carbon removal
• Agriculture and food processing

• Graduate Students and Researchers, Scientists and Engineers (materials scientists, physicists, electro-chemists, nano-scientists, nuclear scientists and engineers)
• Investors
• Entrepreneurs to develop the science into products 
• Government policy makers