Nanowerk March 20, 2023 The nonlinearity provided by the atom leads to a strong dependence of the light–matter interface on the number of photons interacting with the two-level system within its emission lifetime. This nonlinearity unveils strongly correlated quasiparticles known as photon bound states, giving rise to key physical processes such as stimulated emission and soliton propagation. Although signatures consistent with the existence of photon bound states have been measured in strongly interacting Rydberg gases their hallmark excitation-number-dependent dispersion and propagation velocity have not yet been observed. An international team of researchers (Switzerland, Australia, Germany) has reported the direct observation […]
Tag Archives: Quantum technology
A new way for quantum computing systems to keep their cool
MIT News February 21, 2023 To overcome errors in the qubits due to heat in quantum systems, researchers at MIT developed a wireless communication system that enables a quantum computer to send and receive data to and from electronics outside the refrigerator using high-speed terahertz waves. A transceiver chip, cryostat, placed inside the fridge sends and receives data from a terahertz wave source outside the cryostat using backscatter. An array of antennas on top of the chip, each of which is only about 200 micrometers in size, act as tiny mirrors. These mirrors can be “turned on” to reflect waves […]
Entangled atoms cross quantum network from one lab to another
Science Daily February 2, 2023 Trapped ions are one of the leading systems to build quantum computers and other quantum technologies. To link multiple such quantum systems, interfaces are needed through which the quantum information can be transmitted. An international team of researchers (Austria, USA – Georgetown University, Switzerland, France) has demonstrated an elementary quantum network of two atomic ions separated by 230 m. The ions were trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion was entangled with the polarization state of a single cavity photon; […]
Researchers devise a new path toward ‘quantum light’
Science Daily February 2, 2023 Strongly driven systems of emitters offer an attractive source of light over broad spectral ranges up to the X-ray region. A key limitation of these systems is that the light they emit is mostly classical. An international team of researchers (USA – Harvard University, MIT, UK, Israel, Austria) overcame this constraint by building a quantum-optical theory of strongly driven many-body systems, showing that the presence of correlations among the emitters creates emission of non-classical many-photon states of light. They considered the example of high-harmonic generation, by which a strongly driven system emits photons at integer […]
Scientists realize faster method for quantum key distribution
Phys.org February 8, 2023 In the past two decades, quantum key distribution networks based on telecom fibers have been implemented on metropolitan and intercity scales. One of the bottlenecks lies in the exponential decay of the key rate with respect to the transmission distance. Recently proposed schemes mainly focus on achieving longer distances by creating a long-arm single-photon interferometer over two communication parties. Despite their advantageous performance over long communication distances, the requirement of phase locking between two remote lasers is technically challenging. By adopting the recently proposed mode-pairing idea, researchers in China have demonstrated high-performance quantum key distribution without […]
Toward practical quantum optics: Multiphoton qubits from LNOI
Phys.org February 8, 2023 The large-photon-number quantum state is a fundamental but nonresolved request for practical quantum information applications. Researchers in China have proposed a N-photon state generation scheme that is feasible and scalable using lithium niobate on insulator circuits. The scheme was based on the integration of a common building block photon-number doubling unit (PDU) for deterministic single-photon parametric downconversion and upconversion. The PDU relies on a 107-optical-quality-factor resonator and mW-level on-chip power, which is within the current fabrication and experimental limits. N-photon state generation schemes, with cluster and Greenberger–Horne–Zeilinger state as examples, are shown for different quantum tasks… read more. […]
New analog quantum computers to solve previously unsolvable problems
Phys.org January 30, 2023 Tuning a material to the cusp between two distinct ground states can produce physical properties that are unlike those in either of the neighbouring phases. A tunable array of coupled qubits should have an appropriately rich phase diagram but realizing such a system with either tunnel-coupled semiconductor quantum dots or metal nanostructures has proven difficult. The challenge for scaling up to clusters or lattices is to ensure that each element behaves essentially identically and that the coupling between elements is uniform, while also maintaining tunability of the interactions. Advances in the fabrication and control of quantum […]
Lab develops new method for on-chip generation of single photon
Phys.org January 17, 2023 Optically active defects in 2D materials, such as hexagonal boron nitride (hBN) and transition-metal dichalcogenides (TMDs), are an attractive class of single-photon emitters. An international team of researchers (USA – UC Santa Barbara, Japan) has demonstrated a novel approach to precisely align and embed hBN and TMDs within background-free silicon nitride microring resonators. Through the Purcell effect, high-purity hBN emitters exhibited a cavity-enhanced spectral coupling efficiency of up to 46% at room temperature, exceeding the theoretical limit (up to 40%) for cavity-free waveguide-emitter coupling and demonstrated nearly a 1 order of magnitude improvement over previous work. […]
New spin control method brings billion-qubit quantum chips closer
Phys.org January 12, 2023 The electron spin forms a qubit that is naturally robust to electric fluctuations. However, a common control strategy is the integration of micromagnets to enhance the coupling between spins and electric fields, which, in turn, hampers noise immunity and adds architectural complexity. An international team of researchers (Australia, Japan, Germany, Canada) used switchable interaction between spins and orbital motion of electrons in silicon quantum dots, without a micromagnet. The weak effects of relativistic spin–orbit interaction in silicon were enhanced, leading to a speed up in Rabi frequency by a factor of up to 650 by controlling […]
Chip circuit for light could be applied to quantum computations
Phys.org January 3, 2023 While substantial progress has been made, separately, towards ultra-low loss chip-scale photonic circuits and high brightness single-photon sources, integration of these technologies has remained elusive. An international team of researchers (USA – National Institute of Standards and Technology, University of Maryland, research org., MIT, UC Santa Barbara, industry, Brazil, South Korea) integrated a quantum emitter single-photon source with a wafer-scale, ultra-low loss silicon nitride photonic circuit to demonstrate triggered and pure single-photon emission into a Si3N4 photonic circuit with ≈ 1 dB/m propagation loss at a wavelength of ≈ 930 nm. They observed resonance fluorescence in the strong drive regime, showing promise […]