DOW-UAP-D153: Quantum Tomography of Negative Energy States in the Vacuum - Homodyne Detectors, Squeezed Light and the Casimir Cavity

Source file: DOW-UAP-D153_AAWSAP-DIRD-Quantum-Tomography-of-Negative-Energy-States-in-the-Vacuum-January-11-2011.pdf Originating agency: Defense Intelligence Agency (DIA), Defense Warning Office; written under the AAWSAP program Document type: Defense Intelligence Reference Document (DIRD), labelled "Defense Futures"; control number DIA-08-1102-007 Date: 11 January 2011 (information cutoff date, ICOD: 10 August 2010) Classification: UNCLASSIFIED//FOR OFFICIAL USE ONLY (the FOUO marking is struck through on the copy released in 2026) Page count: 51 VIRIN: 260918-D-D0360-1142 PURSUE Release: 6

Summary

"Quantum Tomography of Negative Energy States in the Vacuum" is the last DIRD in the series released under PURSUE, and the latest by date. According to the inside cover it was prepared by the Technology Warning Division (DWO-4) of the DIA's Defense Warning Office, and the author's name has been replaced with the label "AAP Person 58". The body runs to 47 numbered pages (PDF pages 5 to 51) and consists of an introduction, three main sections, a conclusion, acknowledgements and a 60-item reference list, with 20 figures and 17 numbered equations.

The argument is simple: "exotic" propulsion through wormholes or warp drives requires negative energy; laboratories already produce tiny amounts of it, in squeezed light and in the Casimir effect; but you cannot control what you cannot measure. So, the paper argues, the first step is to develop tools that measure and map negative energy in space and time, and the tool it proposes is quantum optical homodyne tomography, an established technique in experimental quantum optics.

Unlike the preceding DIRD in the series, DOW-UAP-D153 ends with practical recommendations: a research and development programme, portable "commercialized" detectors, and sensor arrays for the "surveillance and detection of any anomalous aerospace platforms". This is the closest the paper comes to the subject of unidentified phenomena; the terms UFO and UAP do not appear in it at all.

Research Article

The document and its place in the series

The cover carries the date 11 January 2011, an information cutoff date (ICOD) of 10 August 2010, the control number DIA-08-1102-007 and the label "Defense Futures" (page 1). The administrative notes on page 2 describe the paper as "one of a series of advanced technology reports produced in FY 2010" under the "Advanced Aerospace Weapons System Applications (AAWSA) Program", and direct questions to AAP Person 1, "AAWSA Program Manager", at ATTN: JUIAF - DI/DWO-3, Bldg. 6000, Washington D.C. 20340-5100. The printed page numbers run four lower than the PDF page numbers; this article uses PDF page numbers.

The paper was written eight days after DOW-UAP-D152 ("Negative Mass Propulsion", 3 January 2011). Both deal with "negative" quantities, but with different concepts: D152 concerns the negative mass of matter, while D153 concerns the negative energy density of quantum fields, a phenomenon mainstream physics recognises at tiny scales. Of the program's technical areas, the paper serves propulsion and "spatial/temporal translation", since it opens explicitly with wormholes and warp drives, and to a lesser degree lift ("levitation via antigravity"). In practice most of it is about measurement instrumentation.

Its character as a synthesis shows in its materials too: almost every figure appears "courtesy of" outside researchers, and on the acknowledgements page the author thanks Professors Ulf Leonhardt and Piotr Marecki for "lecture notes, references, and experimental data" (page 49).

What "negative energy" is, and why propulsion designers care

The introduction opens with a vision: "Future aerospace vehicles could have an advanced propulsion system that uses negative quantum vacuum energy to modify the spacetime geometry" around the vehicle, producing faster-than-light motion through traversable wormholes or warp drives, "or even levitation via antigravity" (page 5). According to the paper, these concepts are "well-known in mainstream general relativity and quantum field theory research".

The first main section, "REVIEW OF NEGATIVE (or SUB-VACUUM) ENERGY", explains "exotic matter": matter whose energy density is negative, or smaller than its pressures and tensions. The energy conditions of general relativity formulated by Hawking and Ellis (the weak, null, dominant and strong energy conditions: WEC, NEC, DEC and SEC) forbid such matter, but according to the paper they are "mere hypotheses". It was discovered as early as 1965 that quantum field theory allows local regions of negative energy density, and the paper adds a sweeping claim: all the energy-condition hypotheses have been tested in the laboratory and "shown to be false - 25 years before their formulation" (page 8). In quantum field theory, it explains, negative energy is a manifestation of "sub-vacuum" levels of the vacuum's zero-point fluctuations, that is, states in which the fluctuations are smaller than those of the ordinary vacuum.

The paper lists five examples of "exotic" fields known in nature: static electric or magnetic fields, squeezed vacuum states, "gravitationally squeezed" vacuum fluctuations, the Casimir effect, and other quantum states such as superpositions of electron states. It chooses to deal with only two of them, squeezed light and the Casimir effect, "due to their ready applicability and technical maturity", and sets the rest aside as "theoretical curiosities" (page 9).

The two laboratory examples: squeezed light and the Casimir effect

After a short tutorial on the quantum field theory of light, including the history of zero-point energy (Planck in 1912, Einstein, Hopf and Stern in 1913, and Mulliken's spectroscopic evidence of 1924, page 12), the paper explains "squeezing": reducing quantum noise in one variable at the expense of increasing it in the conjugate variable. A nonlinear crystal such as KTP or lithium niobate is "pumped" by a laser at twice the frequency and behaves, in an image the paper offers, like a swing amplified by changing its length (page 15). The result is a wave whose energy density oscillates between positive and negative values: by a formula from Pfenning (equation 9), it falls below zero once every cycle for any nonzero squeezing parameter, while its time average stays positive (pages 14 to 16). Figure 1 shows this as a curve whose blue "troughs" are the negative-energy pulses (page 17).

The Casimir effect is, according to the paper, "by far the easiest and most well known way to generate (static) negative energy in the lab" (page 17): a tiny attractive force between two neutral, parallel conducting surfaces in a vacuum, arising from a difference in zero-point energy density between the gap and the space outside. The energy density between the plates is given by an expression whose coefficient in four-dimensional spacetime is π²/720, and it scales inversely with the fourth power of the separation (page 18). The paper also mentions the "dynamical Casimir effect" of an accelerating mirror, but dismisses it as "exceedingly small" (page 19).

Homodyne tomography: reconstructing a quantum state from its "shadows"

The second main section begins with a reservation about 2002 work by Davies and Ottewill, who calculated how a theoretical particle detector would respond to negative energy (in their model, it would "cool"). "It is curious that Davies and Ottewill did not consider using quantum optical homodyne tomography as a tool to test their hypothesis, because this is already a mature experimental discipline," the author writes (page 20).

Nearly 20 pages (20 to 36) are devoted to a tutorial on the technique. Tomography, "from the Greek word for slice", infers the shape of a hidden object from its shadows at different angles. In the quantum version the hidden object is the Wigner function, a phase-space description of the quantum state which, unlike an ordinary probability distribution, can take negative values. Figures 4 to 7 show experimentally reconstructed Wigner functions: the vacuum, a coherent state, a squeezed vacuum, a single photon and "Schrodinger cat" states, which because of their small size are called "Schrodinger kitten states" (pages 23 to 28). The paper even pauses to explain Schrodinger's 1935 thought experiment, with its hydrocyanic acid and radioactive atom.

The components are then explained: the beam splitter, whose "empty" input port still admits vacuum fluctuations; photodiodes of silicon (out to a wavelength of one micrometre) and InGaAs; and finally the balanced homodyne detector (BHD), in which the signal is mixed at a 50:50 beam splitter with a strong laser beam, the "local oscillator", and the two photodiode currents are subtracted. The difference is proportional to a quadrature of the field, and the local oscillator amplifies the signal until even noisy photodiodes reach single-photon resolution (pages 31 to 33). Repeating the measurement at many phase angles allows the Wigner function to be reconstructed.

Two instruments: a time-domain detector and a detector inside a Casimir cavity

The third main section turns to experiments. Squeezed light, "darker than vacuum", was first observed in experiments by Slusher and collaborators and reported by Robinson in the mid-1980s. The paper gives figures from an experiment by Schneider and colleagues (1998): an optical parametric amplifier pumped by a 532-nanometre laser at 380 milliwatts, with a maximum noise reduction of 6.5 dB, an average reduction of 6.2 dB over 14 minutes, and 7.2 dB of squeezing in the emitted wave (page 37). Most measurements, it notes, were made in the frequency domain, usually at 5 to 10 MHz, and therefore give information only about a narrow sideband.

The answer is a time-domain detector. The device of Hansen and colleagues (2001) achieved common-mode suppression of more than 85 dB, electronic noise of 730 electrons per pulse, a 14 dB signal-to-noise ratio at repetition rates up to 1 MHz, reconstruction of a coherent state with 99.5% fidelity and 91% quantum efficiency (page 38). Figure 14 shows a measurement of a squeezed vacuum in which the valleys at negative dB values are sub-vacuum regions (page 39).

The second instrument has not yet been built: "What has not been experimentally measured yet are the sub-vacuum fluctuations and their (negative) energy density inside a Casimir cavity" (page 40). In 2008 Piotr Marecki proposed placing a balanced homodyne detector inside a Casimir cavity with plates one micrometre apart, using photodiodes of submicrometre width and submillimetre length, with the cavity's own TE1 mode serving as the local oscillator (Figures 16 to 18, pages 43 to 45). By his calculations, the spectral density of the field fluctuations vanishes below a certain frequency and jumps at its multiples (Figure 19), and in some regions the fluctuations are suppressed by at least 3 dB relative to the ordinary vacuum (Figure 20, page 46).

This is where the Quantum Inequalities come in, a theorem by which a region of sub-vacuum fluctuations must be accompanied by a region of enhanced fluctuations, so that "sub-vacuum fluctuations, and their corresponding sub-vacuum (negative) energy density, cannot persist for long times" (page 46). The paper notes that this has been verified only for single-mode squeezed light, and that several investigators have identified "serious theoretical shortcomings" in the theorem, and so it sees the proposed experiment as a possible test of it.

The recommendations: portable detectors and a "sensor array"

In the conclusion (pages 47 to 48) the author restates the central point: "We already make small amounts of sub-vacuum (negative) energy in the laboratory via the Casimir effect and squeezed light, but we do not yet know if we can access larger amounts for extended periods of time over extended spatial distributions." The author concedes that the Quantum Inequalities suggest producing large amounts "may not be possible", but adds that the claim is untested by experiment.

The recommendations run along two parallel tracks. On the first, a research and development programme would adapt the time-domain detector to measure the energy density of individual pulses directly, followed by an effort to "develop and commercialize a portable time-domain BHD device" to map the negative energy produced by a "putative pulsed (or 'AC') negative energy generator". On the second, an experimental programme would test Marecki's detector and the Quantum Inequalities, followed by a portable "modified-Marecki BHD" for a putative static ("DC") generator. The author adds a caveat: the Casimir effect is so feeble that future propulsion systems will not use Casimir cavities.

Both tracks end with almost the same sentence: such detectors could be assembled into a sensor array "for surveillance and detection of any anomalous aerospace platforms that might use engineered spacetime effects for propulsion" (pages 47 and 48). This is the only place in the paper where the intelligence question, detecting aircraft with unexplained capabilities, is raised explicitly.

What the paper does not say, and an internal inconsistency

The paper does not use the words UFO, UAP or "unidentified phenomenon", describes no case or sighting, and does not claim that any such platform has ever been observed. "Anomalous aerospace platforms" appear only as a hypothetical target for a future sensor array. It gives no estimate of how much negative energy a wormhole or warp drive would need, no timeline and no cost estimate. It presents no original experimental results: all its data and figures come from other people's work. The word "putative" attached to the "negative energy generator" signals that no such generator exists.

The paper also contradicts itself on Marecki's position. On page 46 it reports that he claims, in a 2010 private communication from Leipzig University, that the Quantum Inequalities "should also apply" to the static fluctuations inside a Casimir cavity. On page 48 it says that "Marecki also discovered that the sub-vacuum (negative) energy density regions inside a Casimir cavity violate the Quantum Inequalities theorem." The two statements cannot both be right.

In terms of mainstream physics, the Casimir effect has been measured (the paper cites measurements from 1997, 1998 and 2004) and squeezed light is a routine laboratory technique, so the existence of tiny, local negative energy densities in quantum field theory is not in dispute. What has not been demonstrated is negative energy density at macroscopic scale and over long periods, which is exactly what wormholes and warp drives would need. The paper's statement that the energy-condition objection is "a spurious issue" (page 7) reflects one side of a theoretical debate, a debate the paper itself acknowledges when it describes the Quantum Inequalities as an unresolved constraint.

Significance

D153 is one of the most scientifically grounded of the DIRDs, because most of it describes existing technology and published measurements: homodyne detectors, squeezed light and experimentally reconstructed Wigner functions. The speculation is concentrated in the opening and the close, in framing the research as a first step toward propulsion by engineered spacetime. That is also the difference from D152: there the speculation is at the heart of the paper, here it is the wrapping.

Its particular significance for the PURSUE archive lies in the two nearly identical sentences that close the conclusion. They show that in late 2010 and early 2011 at least one of the program's authors was thinking not only about future U.S. propulsion but also about sensors to detect "anomalous aerospace platforms" using it, that is, about the detection question at the heart of the interest in unidentified aerial phenomena. The paper offers no evidence that such platforms exist, but it documents the reasoning that, inside AAWSAP, linked theoretical physics to an intelligence-collection task.

Key People

Locations

Key Concepts

Notable Quotes

"Future aerospace vehicles could have an advanced propulsion system that uses negative quantum vacuum energy to modify the spacetime geometry in the immediate vicinity surrounding the vehicle in order to induce faster-than-light motion via traversable wormholes or warp drives, or even levitation via antigravity." -- page 5

"This is a necessary first step to take before beginning any study on producing large quantities of negative energy because we will first need to know how to measure and spatially map negative energy in order to properly control it after producing it." -- page 5

"However, all of the energy condition hypotheses have been experimentally tested in the laboratory and experimentally shown to be false - 25 years before their formulation." -- page 8

"It is curious that Davies and Ottewill did not consider using quantum optical homodyne tomography as a tool to test their hypothesis, because this is already a mature experimental discipline." -- page 20

"A major consequence of this theorem is that sub-vacuum fluctuations, and their corresponding sub-vacuum (negative) energy density, cannot persist for long times." -- page 46

"A number of modified time-domain BHD devices could also be assembled in a sensor array for surveillance and detection of any anomalous aerospace platforms that might use engineered spacetime effects for propulsion." -- page 47

"Marecki also discovered that the sub-vacuum (negative) energy density regions inside a Casimir cavity violate the Quantum Inequalities theorem." -- page 48

"Because the Casimir effect and its associated negative energy are incredibly feeble, such putative propulsion systems will not involve the use of Casimir cavities to produce a free-space distribution of negative energy surrounding the platform." -- page 48