On Earth, we use satellite communication using e-m waves and exchange the information with the speed of light i.e., 1,86,000 miles per second. In the deep space this speed introduces time delay owing to the vast distances between the communicating nodes.

Time delay being integral part of e-m based communication system which is actually a to and from travelling time of an e-m waves by virtue of its speed. This time delay can’t be reduced. But we can reduce the length of sentences/paragraphs using coded version thereby reducing the length of time that would otherwise be taken by the full-length sentences/paragraphs. It still remains impractical in deep space communication.

A quantum entanglement property may play a vital role in the deep space communication.

Using this method an instantaneous communication can be established.

Quantum entanglement occurs when a system of multiple particles in quantum mechanics interact in such a way so that the particles cannot be described as independent systems but only as one system as a whole. Measurement (e.g., the spin of an entangled electron) may instantaneously affect another electron's spin at an arbitrarily distant location, apparently (but not actually) faster than the lightspeed limit of special relativity. The fact that electron spin measurements can be highly correlated, violating Bell's inequality, is one of the cornerstone experimental results in the modern theory and interpretation of quantum mechanics.1

Quantum communication is one of the applications of quantum physics and quantum information. There are some famous theorems such as the no-cloning theorem that illustrate some important properties in quantum communication.1

Dense coding and quantum teleportation are also applications of quantum communication.1

Entangled states are key resources to facilitate many quantum information processing tasks and quantum cryptographic protocols.

Here we suggest a nave approach using quantum entanglement property and introducing “Deep space communication vocabulary” concept.

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Rahul Gedamkar

Thursday, 18 November 2021

Nagpur.

The many defining aspects of our modern world — computers, satellites, telecommunications, smart phones, the Internet — currently make use of information that is encoded into classical degrees of freedom.1 

As far as the Deep space communication is concern, presently, deep space communications are done at radio frequencies with embedded time delay. The new methods are required to put to use.

Fundamentally physics is quantum mechanical, and so the ultimate form of information is quantum information. Quantum communication is the art of transferring quantum information from one location to another. The main purpose of quantum communications is to provide a scheme to share a string of random numbers using the superposition principle and the theory of measurements in quantum mechanics.2

Quantum entanglement can be used for communication by taking advantage of the unique correlations exhibited by entangled qubits. We can use entangled qubits to create instantaneous agreement on information across very long distances. While quantum entanglement doesn't allow for communication faster than the speed of light, instant agreement can still be used for applications like High Performance Computing (HPC) and ultra-secure communications. 

How can we use entanglement for communication? 

With entanglement, we can communicate directly through an entangled tunnel without the need to transfer data across a network. 

Quantum networks can create entanglement over very long distances.3 

Quantum Supremacy: Systems in which all the particles and their interactions can be controlled to some degree can deliver functionality for sensing, imaging, communications, simulation and computation.4  

Micro-Electro-Mechanical Systems (MEMS):   Low-noise mechanical oscillator sensors which achieve the highest sensitivity in the world for a micromachined inertial sensor, and can detect at the quantum level.5

Quantum Nanophotonics: With nanophotonic, not only do interactions become stronger and faster but also weak effects once difficult to detect are dramatically enhanced. The result is extreme sensing capability, with localised surface plasmonic at the quantum level.5

Folding 2D materials gives them new properties useful for quantum communications6

The WS2 nanomesh doubles the frequency and halves the wavelength of laser light. This means it could be useful in components for quantum communications using light.6 

Quantum communication: So far, secure key distribution between two distant users has been mainly studied and becomes ready for application. Quantum communication has, however, much more potential. For example, multi-party cryptographic protocols, super dense coding, and distributed quantum computation are possible with the help of quantum media transfer.7

Currently most quantum communication links are direct point to point links through telecom optical fibres and ultimately, limited to about 300-500 kms due to loses in the fibre. Experimentally, QKD has been implemented via optical means, achieving key rates of 1.26 megabits per second over 50kms of standard optical fibre and 1.16 bits per hour over 404 kms of ultra-loss fibre in measurement-device-independent configuration.10

Quantum Internet: In addition to point-to-point quantum key distribution, the quantum internet will be able to distribute quantum states between the quantum memories of functional quantum processors.8 

Application of Quantum Entangled States in Quantum Communication 

The applications of entangled states include: quantum teleportation, quantum dense coding, quantum key distribution and so on.  Quantum teleportation is an important example of quantum information processing. As far as teleportation is concerned, the establishment of the maximum entangled state of two distant qubits enables any unknown single bit quantum state to be teleported from one to the other. Quantum dense coding: The method is that the sender and the receiver each have a maximum entangled particle and are in a maximum entangled state. Because the two particles are entangled, any operation on one particle will affect the other particle, resulting in the formation of phase.9 

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 1.Ref.: Home/ Research groups/ Imperial Centre for Quantum Engineering/ Science and Technology/ Research/Quantum Communications

2.Ref.: https://www.frontiersin.org/research-topics/16604/new-horizons-in-quantum-communication

3.Ref.: https://www.aliroquantum.com/blog/quantum-entanglement-communication

4. Ref.: https://www.imperial.ac.uk/quantum-engineering-science-technology/research/quantum-information/#knight

5. Ref.: https://www.imperial.ac.uk/quantum-engineering-science-technology/research/quantum-sensors/

6. Ref.: https://theconversation.com/folding-2d-materials-gives-them-new-properties-useful-for-quantum-communications-new-research-160741

7. Ref.: https://www.nii.ac.jp/qis/first-quantum/e/subgroups/quantumCommunication/index.html

8. Ref.: https://www.mcqst.de/research/quantum-communication

9.Ref.: Quantum Entanglement and Its Application in Quantum Communication To cite this article: Nanxi Zou 2021 J. Phys.: Conf. Ser. 1827 012120

10. Ref.:  https://idstch.com/technology/quantum/quantum-repeater-paves-way-long-distance-big-quantum-data-transmission/

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Rahul Gedamkar

Edited on 25/11/2021     

Saturday, 20 November 2021

Nagpur

Unlike communication in space, communicating between deep space and Earth is far more difficult, as Earth is surrounded by an atmosphere that consists of five layers, each with different characteristics, but all forming an impediment to radio and optical communications. The atmospheric layers absorb and scatter signals within them, reducing signal strength and limiting the specific portions of the electromagnetic spectrum that can be used for communication. Below 30 MHz, the ionosphere layer of the atmosphere absorbs and reflects signals, and above 30 GHz the lower atmosphere or troposphere absorbs them. As a result, the region between (roughly) 30 MHz and 30 GHz is chosen for communications from deep space to Earth. (Ref.: NASA)

Purification of entanglement: In a quantum microwave communication transmission channel, due to a variety of unavoidable natural environment noises, the microwave quality coefficient of "quantum entangled state" will gradually decrease with the increase of microwave transmission channel distance, that is, with the gradual increase of microwave transmission distance, the mutual entanglement between two neutral particles will gradually degenerate. Therefore, the entanglement coefficient will gradually increase and the mass will decrease. It is necessary to adjust the high entangled state from the lowest entanglement "purification" to the lower highest entanglement.

No matter what kind of entanglement operation, decoherence is the biggest obstacle of entanglement operation. Entanglement purification is an effective method to overcome environmental noise and decoherence: it can keep the logarithm of single entanglement high purity. (Ref.: Quantum Entanglement and Its Application in Quantum Communication To cite this article: Nanxi Zou 2021 J. Phys.: Conf. Ser. 1827 012120).

However, farther from Earth, latency can become a challenge. At Mars’ closest approach — about 35 million miles away — the delay is about four minutes. When the planets are at their greatest distance — about 250 million miles away — the delay is around 24 minutes. This means that astronauts would need to wait between four and 24 minutes for their messages to reach mission control, and another four to 24 minutes to receive a response. (NASA)

Finally, vulnerabilities due to theory-practice gaps continue to appear. To address these issues, we need further exploration of scalable technologies such as photonic-integrated chips. Research on adaptation and integration techniques can facilitate quantum-communication-based solutions in real-world network configurations. 

Quantum communication: 

• Quantum communications is different than quantum computing. 

• All quantum technologies manipulate quantum properties of small particles for practical uses. 

• Quantum communications is related to optical communications, and typically utilizes the same wavelengths, hardware, and delivery medium (free-space directional links or fibre optics). But that means it has the same losses and directionality as optical communications, and cannot penetrate clouds or walls like RF. 

Quantum technologies:

Quantum Computing

Quantum communication

QKD

Quantum Clock Synchronization

QRNG

Quantum Networking

Quantum Metrology

The main efforts are being taken for the secure communication utilising quantum properties.   

At its core, quantum communication processes are based on either a prepare and measure or entanglement-based protocols.

Prepare-and-Measure protocol is BB84 (after the paper written by Charles Bennett and Gilles Brassard in 1984), which relies on the uncertainty principle and the quantum no-cloning theorem. Prepare-and-Measure has been demonstrated with low power lasers that emit very small numbers of photons (ideally, one) per pulse. Because of this, Prepare-and-Measure is also known as weak coherent pulse. Only Alice and Bob know the correct polarization to measure

Entanglement-based protocols (such as E91, named after the 1991 Artur Ekert paper) takes advantage of quantum entanglement. Pairs of entangled photons are created and sent to Alice and Bob, who measure their correlated properties.

Entanglement does not require encoding states into the photons. Instead, both parties share a source of maximally entangled photon pairs, which is a truly random process. The distribution of entangled photons necessary for this process is also the foundation for a truly quantum network. Shared entanglement is a basic resource for quantum teleportation and other applications of what could loosely be called the quantum internet.

Quantum clock synchronization (QCS), in contrast, exploits the femtosecond-level correlations between pairs of entangled photons to provide accuracy. QCS also exploits two other quantum properties, the Quantum No-Cloning Theorem and Entanglement, to ensure that an adversary (enemy, rival) cannot receive a quantum signal and retransmit it.

The QCS protocol starts with two remote parties, Alice and Bob, with an unknown time delta between them. Each of them has an entangled photon source and receiver and the ability to link through free-space or fibre optic. Alice sends one of the photons of each entangled pair produced at her side to Bob and measures the other one according to her local clock. Bob performs the same operations on his side. Alice and Bob also each measure the time of arrival of incoming photons. They then share the times of arrival of the measured photons. Processing the data via a cross-correlation provides the time delta between their clocks (irrespective of distance between them). They also do a check to guarantee that the signal was not spoofed.

The value of quantum communications is primarily due to its security. The main focus of development of technologies in quantum communication is to make absolutely secure communication. At Global level it is an essential feature to protect the data from eavesdropping.  (spying) 

However, in deep space an instantaneous communication is the practical requirement. Entanglement property is required to be harnessed in this direction. It is our motto and point of focus too. 

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Rahul Gedamkar

Thursday, 25th November 2021

Nagpur

If A makes measurement corresponding to vocabulary following the protocol; B’s detector detects it immediately and system collapses from entanglement (super position state) to pure state corresponding to vocabulary as per protocol. In this system the information is stored at both places viz A and B. Using entanglement property, we can restore the information corresponds to the identified vocabulary.

In fact, actual sending of the information bits and receiving of the information bits do not take place thereby not violating the no-communication / no cloning / no broadcasting etc. theorems. 

Faster than light communication possible without violating FTL.

Different entangled states are required to be developed and corresponding Protocol too. 

1. Measurement/interaction be made as per pre-defined systematic form and protocol. The different combinations may be assigned the codes.

 e.g., A, B, C & D and correspondingly A’, B’, C’&D’. i.e., vocabulary.

2 3 4 1 → B 2’ 3’ 4’ 1’ → B’

3 4 1 2 → C 3’ 4’ 1’ 2’ → C’

4 1 2 3 → D 4’ 1’ 2’ 3’ → D’

1 2 3 4 → A 1’ 2’ 3’ 4’ → A’

ALICE’s pattern                                                          BOB’s pattern

2. By looking/analysing the pattern (circuit design is to be developed) and using CODEC (coding – decoding circuit), pre-assigned pattern can be obtained, without sending the actual information, which is not possible by the virtue of “NO communication theorem”.

3. Different combinations of the entangled states are required to be produced.

For deep space communication, identification of information at distant node is a new approach. It involves detection of quantum state(s) after measurement and inevitable collapse of superposition state (i.e., composite states or indeterminant state). Various models are required to be developed and put to test.

A current approach is to transfer of information in absolutely secure way through the entanglement. It poses embedded constraints of FTL and quantum theorems.

Avoiding the transfer of information, ruled out the FTL and various theorems. Similarly, quantum cryptography finds no place in such system owing to no transfer of information and tremendous vast distances in deep space. 

The current technical advances and continued research on various aspects of quantum entanglement can be appropriately applied to achieve the development of vocabulary of information as if the ‘Directory’ in those days of Telephone era; and the identification technic of the vocabulary using entanglement property thereof.

Once it is achieved, the instant communication can be established in real time in deep space.

This instantaneous communication has limitation of contents of vocabulary.

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Rahul Gedamkar

Edited on 25/11/2021

Thursday, 18 November 2021

Nagpur.