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# The Daily Qubit

## 🕳️ Quantum tech takes on space-time. Plus, magic was the secret all along and quantum algorithms are making your next flight a breeze.

# Welcome to the Quantum Realm.

🕳️ *Quantum networks takes on space-time — experimentally realized interplay of quantum theory and general relativity. Plus, magic was the secret all along and quantum algorithms are making your next flight a breeze. *

## 🗓️ UPCOMING

**Sunday, July 7 |** **QTM-X Quantum Education Series 6 of 10**

## 📰 NEWS QUICK BYTES

So it turns out we can just use magic to reach quantum supremacy: Based on phenomena first theorized in 2009 and experimentally observed in 2017, researchers have recently found that a "quantum switch" can increase the computational power of quantum computers by introducing indefinite causal order (event A can cause event B and vice versa). The team from Hong Kong University of Science and Technology developed a mathematical model demonstrating how this switch enhances the "magic" of qubits — not that kind of magic, but rather a key property that fuels quantum computing capabilities. This suggests that applying the quantum switch could enable quantum computers to reach quantum advantage. But don’t get too excited just yet; practical implementation poses challenges, of course, though the team is optimistic about future experiments with photonic qubits.

Good news for frequent travelers — quantum algorithm for optimizing airport operations: The University of Hamburg's Institute for Quantum Physics and Lufthansa Industry Solutions are working on implementing quantum algorithms to optimize airport gate assignments, which is a complex logistical challenge faced by airports globally. Dieter Jaksch, a quantum physicist at UHH, remarks on the ability of quantum computers to explore billions of possible solutions, which makes them well-suited for managing large airports with numerous gates and flights.

NATO’s Transatlantic Quantum Community has officially launched: The Transatlantic Quantum Community held its inaugural virtual meeting in Brussels this past Tuesday, following NATO Secretary General Jens Stoltenberg's call for a dedicated quantum network to enhance Allied cooperation. The TQC, led by NATO but with voluntary participation, includes over half of the Allies, such as the U.S., Canada, France, Italy, and Czechia, with Denmark as the first chair. The Community is on a mission to unite quantum experts from various sectors to address funding and technology challenges, foster talent, and encourage innovation, ensuring NATO maintains its technological edge in security. The first annual plenary of the TQC is scheduled for this coming autumn.

Fujitsu and ANU partner to establish quantum research center in Australia: Fujitsu Australia and the Australian National University have signed an MoU to create a world-class quantum research center in Canberra, featuring an onsite quantum computer. This partnership aligns with Australia's National Quantum Strategy to promote quantum research and industry by providing access to quantum technologies as well as training for industry professionals, researchers, and students. Fujitsu will also offer ANU access to its quantum systems and simulators in Japan, with plans to release a 256-qubit quantum computer in March 2025 and a 1000-qubit system by fiscal year 2026.

On the future growth and importance of quantum communication technologies: A new study by Fraunhofer ISI and Saarland University explores the evolution of quantum communication technologies and their part in providing secure communication. The study analyzes three generations of quantum communication: market-ready quantum key distribution using prepare & measure principles, less mature QKD with photonic entanglement, and the developing quantum repeaters for long-distance entanglement distribution. The research calls out Europe’s leading role in patent activities and predicts strong market growth with annual rates of 15-25%.

Taiwan seeking additional quantum cooperation with Finland and France: A Taiwanese delegation led by the National Science and Technology Council recently visited Finland and France with the goal of encouraging collaboration in quantum technology. Key stops included the Inside Quantum Technology Nordics Helsinki event where NSTC officials highlighted Taiwan's semiconductor expertise. The delegation engaged in workshops with Finnish counterparts and met with prominent French R&D institutions and quantum startups. To further promote international cooperation, NSTC will host the Quantum Taiwan 2024 conference in October, inviting experts from Japan, France, and other partner countries.

## How many qubits was today's newsletter? |

## ☕️ FRESHLY BREWED RESEARCH

Testing quantum theory on curved space-time with quantum networks: Quantum networks and entangled clocks are used to experimentally observe the interplay between quantum theory and general relativity on curved space-time. By leveraging photon-mediated entanglement, the study enables non-local measurements that allow for the observation of interference patterns resulting from the superposition of different proper times experienced by entangled clocks in a gravitational field. This is truly a novel approach that provides empirical evidence of how quantum states evolve under the influence of space-time curvature. Breakdown here.

Lattice-Based Quantum Advantage from Rotated Measurements: An optimized protocol for quantum cryptography is introduced. The protocol leans on the hardness of the learning with errors problem to perform cryptographic tasks using classical communication and a quantum device. It presents a two-round proof of quantumness and a one-round protocol for blind remote state preparation, enhancing security and efficiency while reducing quantum resource requirements. Breakdown here.

Integrating quantum computing resources into scientific HPC ecosystems: An exploration of the integration of quantum computing as an accelerator within classical HPC systems proposes a hardware-agnostic framework. Through detailed analyses, benchmarks, and code optimization, the framework seeks to encourage scientific discovery in fields like quantum chemistry, optimization, and artificial intelligence by combining the two capabilities.

DRLQ: A Deep Reinforcement Learning-based Task Placement for Quantum Cloud Computing: DRLQ is a deep reinforcement learning-based technique for task placement in quantum cloud computing environments that uses the Rainbow DQN approach to optimize task completion time and scheduling efficiency. Extensive experiments using the QSimPy simulation toolkit demonstrate that DRLQ reduces total quantum task completion time by 37.81%-72.93% and minimizes rescheduling attempts as compared to traditional heuristic methods.

Machine Learning Accelerates Precise Excited-State Potential Energy Surface Calculations on a Quantum Computer: An approach that integrates deep neural networks with variational quantum algorithms is used to expedite the calculation of excited-state potential energy surfaces on quantum computers. By using DNN-assisted variational quantum deflation and subspace search variational quantum eigensolver methods, the authors significantly reduce computational time and improve accuracy in predicting excited-state properties of small molecules, such as ArF, LiH, and HeH+.

Collective advantages in qubit reset: effect of coherent qubits: An investigation of the collective advantages of qubit reset in quantum computing focuses on the thermodynamic cost and error probabilities associated with resetting multiple coherent qubits using the Dicke state. The authors demonstrate that collective reset processes significantly reduce heat production and error probabilities compared to parallel resets.

## UNTIL TOMORROW.

### BREAKDOWN

**Testing quantum theory on curved space-time with quantum networks**

🔍️ **SIGNIFICANCE:**

The unification of electricity and magnetism as well as the unification of the electroweak force might imply that nature tends toward elegance and unification. As beings that respond well to order, we’ve even taken it a step further in seeking out a singular, underlying truth that perfectly integrates all aspects of the universe. This is why one of the fundamental tasks in theoretical physics is to unify quantum theory and general relativity. For our own sanity, yes, but also because the inconsistency of both concepts at the Planck level suggests the two need each other.

While general relativity has been observationally verified through the LIGO detection of gravitational waves, imaging of the event horizon of a black hole, and the existence of GPS technology which uses relativity to correct for time dilation, the intersection of quantum theory and relativity has yet to be fully experimentally explored.

However, quantum technology is allowing us to explore these phenomena further, such as through the use of entangled clocks to test quantum theory on curved space-time. In entangled clocks, the superpositions of different proper times results in measurable interference patterns which provide us direct evidence of how quantum states evolve under the influence of space-time. Classical sensors have been unable to achieve this previously as they are unable to account for the superposition or entanglement of quantum states.

This research adapts this to quantum networks to use photon-mediated entanglement for non-local measurements that allow us to observe the interference patterns of entangled clocks in a gravitational field. The presence of interference results from the superposition of different proper times on the clocks, and the different proper times result from gravitational time dilation, effectively providing us an experiemental environment where evidence of both can be observed.

🧪 **METHODOLOGY:**

Single photon emission and detection is used to generate entanglement between atomic systems. For state preparation, atoms are initially prepared in specific quantum states and then entangled through photon interactions.

Non-local clock states evolve under different proper times in a gravitational field. The interference patterns from photon emissions are used to study how time and space affect the clocks.

Using atoms such as Strontium or Ytterbium is advantageous due to their long coherence times which means they can maintain their quantum states for an extended time without information loss. These advanced atomic systems allow for the scalability to larger setups and more complex configurations.

📊 **OUTCOMES & OUTLOOK:**

Perhaps one of the most interesting results from this study, from the perspective of the advancement of quantum information science, is that proper time interferometry can be extended to quantum networks and effectively allow experiments that span kilometers.

The occurrence of both interference patterns and proper time differences provided empirical evidence for the interplay between quantum theory and general relativity.

**Research Inspiration:**Looking forward, the implication is that quantum networks may be a powerful tool for exploring fundamental physics, especially in the theoretical realm, as well as continuing to uncover the quantum nature of gravity.

^{Source:}^{ Johannes Borregaard and Igor Pikovski. Testing quantum theory on curved space-time with quantum networks.}^{ arXiv quant-ph}^{. (2024). }^{https://doi.org/10.48550/arXiv.2406.19533}

### BREAKDOWN

**Lattice-Based Quantum Advantage from Rotated Measurements**

🔍️ **SIGNIFICANCE:**

Traditionally, quantum cryptography assumed that quantum states would be transmitted between two different parties for cryptographic tasks. But recently, studies have shown that if one party has a particularly powerful quantum device, these cryptographic tasks can be performed through classical communication while still taking advantage of quantum properties. This is significant since our current global communication systems are based on classical computing. While the aforementioned powerful quantum computing device is still a ways off on the roadmap, the idea that we could leverage current infrastructure would be a relief for governments and cryptoanalysts everywhere, I’m sure.

In order for this to work, there are a few things that need to be taken into consideration. First, in our two-party system, we are assuming one has access to a powerful quantum device. This is verified through “Proof of Quantumness,” in which a classical verifier requests computations from the alleged quantum verifier. This typically involves an NP-hard problem that, while difficult for both devices, the quantum device can solve at a noticeably improved rate as compared to the classical verifier. While proof of quantumness based on trapdoor claw functions is not novel, there are a few differentiations proposed in this protocol. Instead of previous methods which required preparing, measuring, and retaining quantum memory of three claw states, this proposed method only requires one at each iteration. This is an improvement in terms of quantum resources.

The next piece required is remote state preparation where a classical client can delegate the preparation of a quantum state to a remote server. This is considered blind remote state preparation if the server does not learn the classical description of the state in the process of preparing it.

Traditional quantum cryptographic protocols that use TCFs typically involve measurements using the Pauli-x or z operators (which refer to the x and z-axis of the Bloch sphere representation of a qubit). Instead of being limited to the x and z-axis, the proposed protocol instead utilizes the entirety of the xy-plane by measuring rotations around the z-axis. This effectively allows for a broader range of angles, making it more difficult for an adversary to predict. As a whole, this protocol not only improves security but also reduces complexity as compared to previous recommendations.

🧪 **METHODOLOGY:**

For the proof of quantumness, Alice (the verifier) generates a public key and secret key using an LWE-based key generation algorithm. Alice encrypts a random bit and broadcasts the public key and ciphertext to Bob (the prover). Bob uses the public key and ciphertext to prepare a superposition state and then measures the qubits of the state in a rotated basis determined by angles in the xy-plane and reports the results to Alice. In the second round, Alice samples another random bit and sends it to Bob. Bob measures his state in the eigenbasis of the rotated measurement and returns the result to Alice.

For the blind remote state preparation, Alice (the client) wants to prepares a quantum state by using an LWE-based encryption scheme and sends the encrypted value along with the public key to Bob. Bob uses the encrypted value to prepare the quantum state by performing rotations around the z-axis (in the xy-plane) and then sends the measurement results back to Alice. Alice uses the trapdoor to decrypt the measurements and determine any phase flip corrections needed. The final state prepared by Bob is adjusted to the desired state, ensuring that Bob has no knowledge of the state.

📊 **OUTCOMES & OUTLOOK:**

The developed protocol’s two-round proof of quantumness allows a verifier to distinguish between classical and quantum provers based on the hardness of the LWE problem. The protocol also enables the preparation of any single-qubit state in the xy-plane with a single round of interaction.

The use of rotated measurements enhances the security of quantum cryptographic protocols by directly tying it to the LWE problem, which is a well-established hard problem in both classical and quantum contexts.

The proof of quantumness protocol provides a more practical method for verifying the quantum behavior of devices, and the one-round protocol for blind remote state preparation offers a more efficient and secure way for classical clients to delegate quantum state preparation to quantum servers, moving closer to minimal requirements for lattice-based proofs of quantumness.

**Research Inspiration:**A recommended next step would be to replace the encryption scheme with a more efficient single bit encryption scheme — other LWE-based encryption schemes such as Ring-LWE and Module-LWE were noted as requiring less quantum computation time.

^{Source:}^{ Yusuf Alnawakhtha, Atul Mantri, Carl A. Miller, Daochen Wang. Lattice-Based Quantum Advantage from Rotated Measurements. }^{Quantum Journal.}^{ (2024). }^{https://doi.org/10.22331/q-2024-07-04-1399}

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